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WILLIAM   DILLER  MATTHEW 


GIFT   OF 
WILLIAM  DILLER  MATTHEW 


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LIBRARY 


THE    PALEONTOLOGICAL    SOCIETY 


CONFERENCE  ON  THE  ASPECTS  Of 
PALEONTOLOGY 


* 


FIRST   ANNUAL   MEETING, 
CAMBRIDGE,  MASS.,  DECEMBER  29,  1909. 


Reprinted  from  the  POPULAR  SCIEHCB  MONTHLY,  June  to  November,  1910. 


WASHINGTON,  D.  C. 
1910 


MATTHEW 
LIBRARY 


THE  PALEONTOLOGIC  EECORD 
THE  PALEONTOLOGICAL  SOCIETY  CONFERENCE  PAPERS 

BY  PROKESSOB  JOHN  M.  CLARKE 

STATE   MUSEUM,   ALBANY,   N.   Y. 

Introductory. — The  birth  of  a  new  society  devoted  to  special  scien- 
tific aims  counts  but  little  for  the  advancement  of  knowledge  and  cul- 
ture in  these  days  of  multiplex  organizations  if  it  fails  to  come  into 
being  and  before  the  world  with  an  adequate  excuse  and  a  clean-cut 
purpose.  The  Paleontological  Society,  which  was  conceived  a  year 
ago  and  born  last  winter  in  Boston  at  the  meetings  of  the  American 
Association,  is  the  outcome  of  a  conviction  on  the  part  of  workers  in 
this  science  that  there  is  a  common  bond  of  interest  among  them  all, 
in  spite  of  the  peculiar  conditions  which  have  stamped  paleontology 
with  their  diversity  and  kept  its  devotees  asunder.  Students  of  this 
science  have  approached  it  along  different  avenues.  Some,  and  chiefly 
those  dealing  with  the  vertebrates,  have  laid  the  foundations  of  their 
work  in  the  living  world;  others,  and  here  chiefly  the  students  of 
invertebrates,  have  made  their  entry  as  geologists  and  have  worked 
their  way  from  beneath  upward  to  the  earth's  surface.  Among  the 
paleobotanists  good  men  have  arrived  through  both  approaches.  As 
an  equipment  for  trustworthy  and  lasting  work,  both  of  these  lines  of 
preparation  have  proved  their  efficiency  and  so  all  arguments  bent  to 
demonstrate  the  superiority  of  the  one  over  the  other  schooling  resolve 
themselves  to  a  conclusion  that  both  are  essential  to  the  best  result. 

Diversity  in  training  and  in  the  field  of  activity  has  led  to  diversity 
of  sympathy,  and  it  seemed,  even  to  those  who  had  long  hoped  for  a 
unification  of  these  interests,  that  it  might  hardly  be  practicable  to 
obliterate  these  cleavage  planes.  The  governing  principles  of  the  sci- 
ence are  common,  the  bearings  of  paleontologic  researches  and  results 
are  the  widest  conceivable  in  their  relation  to  the  problems  of  life, 
whether  past,  present  or  future,  and  it  is  not  likely  that  the  magnitude 
of  the  science  can  be  unduly  stated.  From  some  such  considerations  as 
these,  the  writer,  chosen  as  first  president  of  the  new  society,  endeavored 
to  bring  into  the  foreground  of  the  society's  first  meeting,  by  a  "  Con- 
ference on  the  Aspects  of  Paleontology,"  an  introductory  presentment 
of  some  of  the  broader  factors  and  principles  of  the  science,  and  the 
articles  that  follow  herewith  are  the  partial  outcome  of  this  conference. 
In  every  case  where  practicable,  the  themes  were  presented  by  two 

763058 


2  THE  PALEONTOLOGIC  RECORD 

sneakers  making  their  approach  from  different  fields  of  interest.     The 
an  effort  to  define  and  emphasize  the  common  platform 


^  ...  on.  which  the  'paleontologists  must  stand  together;  even  more  than  this, 
•*i  /*:  it-'wfti  otyitrp'ose  to  declare  at  the  outset  that  the  organization,  though 


the  patron  of  detailed  researches  and  patient  endeavor,  recognizes  that 
the  sole  impulse  which  can  guarantee  its  usefulness  and  maintain  its 
integrity  is  its  devotion  to  a  standard  which  touches  close  on  human 
interests. 

ADEQUACY  OF  THE  PALEONTOLOGIC  RECORD 

BY  PROFESSOR  SAMUEL  CALVIN 

UNIVERSITY   OF   IOWA 

WHEN  or  how  life  began  on  our  planet  no  one  may  be  able  to 
tell  us;  but  that  life  has  been  present  and  has  been  an  impor- 
tant factor  in  the  world's  geological  development  since  before  the  be- 
ginning of  the  Cambrian  is  known  to  the  most  callow  of  embryo  geol- 
ogists taking  his  first  course  at  the  village  high  school.  So  far  as 
relates  to  the  skeleton-bearing,  marine  invertebrates  which  have  lived 
on  floors  of  epicontinental  seas,  there  are  remarkably  complete  records 
of  this  long  history  of  living  things,  the  order  of  their  succession,  their 
migrations,  their  geographic  distribution  during  any  given  portion  of 
geologic  time,  as  well  as  of  the  progressive  and  orderly  modifications 
which  resulted  in  the  extermination  of  decadent  or  unfit  types,  on  the 
one  hand,  or  resulted,  on  the  other  hand,  in  the  advancement  of  certain 
types  and  their  adaptation  to  the  conditions  prevailing  in  the  living 
world  to-day. 

The  zoologist,  confining  attention  to  living  forms,  gets  a  view  of  the 
animal  creation  as  it  exists,  after  ages  of  development  and  modification, 
during  a  fraction  of  a  single  faunal  stage.  The  paleontologist,  while 
unable  to  see  the  beginnings  of  life,  gets  the  broader  view  which  comes 
from  a  study  of  the  organic  world  as  it  has  appeared  during  numberless 
successive  stages.  He  may  trace  the  origin  of  forms  and  note  the  trend 
and  tendency  of  variations  in  ways  denied  the  zoologist.  Neither  the 
depth  of  the  water  nor  the  distance  from  the  shore  at  the  points  where 
the  objects  of  his  study  lived  interferes  with  the  thoroughness  of  his 
explorations.  He  is  not  limited  to  what  he  may  learn  by  taking 
samples  of  the  old  sea  bottom,  here  and  there,  with  a  dredge;  he 
traces  his  life  zones  with  practical  continuity  over  areas  of  continental 
extent. 

The  faithfulness  with  which  the  paleontological  record  has  been 
kept  since  the  beginning  of  the  Cambrian  is  a  matter  of  constant  sur- 
prise. No  organism  was  too  small  for  preservation,  if  only  its  soft 


THE  PALEONTOLOGIC  RECORD  3 

parts  were  supported  or  protected  by  a  stony  skeleton  of  some  kind; 
no  parts  of  the  skeletal  structure  were  too  minute  to  be  kept  practically 
unaltered  to  the  smallest  microscopic  detail;  no  period  of  time  has 
been  so  long  that  the  records  of  the  large  or  the  small  things  of  life 
were  necessarily  obliterated.  The  shells  of  such  minute  and  delicate 
things  as  radiolaria  and  foraminifera,  on  the  one  han'd,  and  that  king 
of  invertebrates,  the  giant  Camaroceras,  on  the  other,  have  all  been 
kept  through  the  ages  with  equal  fidelity.  The  hinge  characters  of 
the  brachiopods,  their  internal  arm  supports,  their  spires  and  loops,  the 
distribution  of  the  ramifying  bloocl  channels  in  the  mantle,  the  surface 
markings  of  every  rank  and  grade  down  to  the  smallest  which  can  be 
observed  only  with  the  lens,  and  the  microscopic  structure  of  the  shell 
itself,  are  other  examples  of  the  faithfulness  with  which  details,  how- 
ever insignificant  in  point  of  magnitude,  have  been  guarded,  protected, 
preserved.  Strangely  enough,  in  respect  to  a  very  large  proportion  of 
the  animal  remains  buried  in  the  ancient  sediments  it  looks  as  if  time 
had  been  standing  still;  it  has  neither  marred  nor  destroyed.  The 
organic  remains  from  the  Ordovician  formations  are  quite  as  perfectly 
preserved  as  those  from  the  Tertiary. 

The  profusion  of  the  life  of  the  ancient  seas  is  as  much  a  source  of 
surprise  as  the  detailed  perfection  of  the  record.  In  the  Mississippi 
Valley  limestones  constitute  a  very  large  proportion  of  the  sedimentary 
rocks,  and  it  is  unnecessary  to  say  that  these  limestones  record  the  life 
and  death  of  countless  myriads  of  organisms.  In  some  cases  the  waters 
of  the  old  seas  were  comparatively  quiet,  and  the  shells  or  other  hard 
parts,  undisturbed  and  unbroken,  remain  in  the  positions  they  occu- 
pied when  the  individuals  they  represent  were  alive.  There  is  a  bed 
of  marly  shale  carrying  many  thin  lenses  of  limestone,  lying  between 
the  Platteville  and  the  Galena,  from  60  to  70  feet  above  the  base  of 
the  Mohawkian,  and  these  lenses  are  made  up  in  large  part  of  un- 
broken brachiopod  shells.  On  the  surface  of  one  of  these  slabs,  in  an 
area  measuring  35  square  inches,  one  may  count  more  than  60  perfect 
specimens  of  Dalmanella  subcequata  and  Orthis  tricenaria.  The  rate 
is  about  290  individuals  to  the  square  foot.  The  number  on  a  square 
mile  of  such  sea  bottom  runs  up  into  the  billions.  The  number  of 
individuals  of  the  species  Pentamerus  ollongus  that  swarmed  on  the 
bottom  of  the  Niagaran  sea  is  strikingly  demonstrated  in  every  paleon- 
tological  museum.  The  wide  geographic  range  of  this  species  is  well 
known;  its  range  in  time  was  such  as  to  make  possible  the  accumula- 
tion of  beds  of  limestone,  70  feet  in  thickness,  from  the  detritus  of 
its  broken  shells.  Like  other  persistent  or  widely  ranging  species,  it 
gave  rise  to  a  very  large  number  of  varietal  forms,  some  of  which  have 
been  described  as  specifically  distinct. 

The  Devonian  formations  furnish  similar  evidence  of  the  wonder- 


4  THE  PALEONTOLOGIC  RECORD 

ful  profusion  of  the  ancient  life  and  help  us  to  appreciate  the  wealth 
of  material  that  the  paleontologist  has  at  his  command.  In  the  quarries 
at  Independence,  Iowa,  there  are  beds  crowded  with  beautifully  pre- 
served forms,  mostly  brachiopods,  as  perfect  to-day  in  every  detail  of 
shell  structure  and  ornamentation  as  when  the  currents  of  life  pul- 
sated within.  A  coral  reef,  no  species  lost,  has  been  cut  into  by  a  small 
intermittent  stream  near  Littleton,  Iowa;  and  perfect  coralla,  wagon 
loads  of  them,  are  strewn  along  the  sandy  channel  a  quarter  of  a  mile 
or  more.  A  successor  to  the  reef  just  noted,  composed  of  different 
species,  the  corals  still  in  place,  may  be  seen  and  studied  on  the  west 
side  of  the  river  opposite  the  village  of  Littleton.  The  state  quarry 
beds  near  North  Liberty  are  simply  cemented  masses  of  brachiopods; 
they  illustrate  the  remarkable  prodigality  of  the  Devonian  life,  but  the 
individuals  are  not  in  good  condition  for  study.  It  is  a  different  case 
that  is  presented  by  the  fossils  in  the  marly  beds  of  the  Lime  Creek 
shales  at  the  exposures  between  Mason  City  and  Eockford.  A  very 
large  proportion  of  the  specimens  here  are  as  perfect  as  when  the 
animals  lived;  and  there  is  a  beauty  and  delicacy  and  exquisite  refine- 
ment about  most  of  them  that  is  scarcely  matched,  certainly  not  sur- 
passed, anywhere  among  fossils  of  any  age  or  time.  More  than  65 
species  occur  in  the  Lime  Creek  fauna,  and  thousands  of  individuals 
of  some  of  the  species,  illustrating  wide  ranges  of  variation,  enrich  the 
museums  of  the  world. 

Along  the  Aux  Sables  River  at  many  points  near  Thedford  and 
Arkona,  Ontario,  there  are  calcareous  shales  containing  a  marine  fauna, 
or  rather  a  succession  of  faunas  which  once  flourished  in  wonderful 
profusion  and  is  still  preserved  in  equally  wonderful  perfection.  Sta- 
tistics and  computations  would  fail  to  give  an  adequate  conception 
of  the  abundance  and  character  of  the  material  here  offered  for  study. 
No  detail  of  the  skeletal  parts  has  been  lost ;  and  as  for  the  number  of 
individuals,  they  are  simply  uncountable.  There  lies  before  me  a 
small  fragment  of  this  old  sediment  having  a  surface  of  less  than  15 
square  inches  and  it  shows  51  identifiable  individual  specimens,  not 
counting  stem  segments  of  crinoids.  The  51  individuals  are  distrib- 
uted among  eleven  species,  and  these  represent  eleven  genera — namely, 
Phacops,  Platyceras,  Tentaculites.,  Spirifer,  CTionetes,  Hederella, 
Ortliopora,  Chcetetes,  Arthracantha,,  Striatopora  and  Aulopora.  Can 
any  bit  of  modern  sea  bottom  of  similar  size  make  a  better  showing? 
Above  and  below  the  Rocky  Glen,  near  Arkona,  from  which  this  speci- 
men came,  there  are  opportunities  to  study  continuous  sections  ap- 
proximately 100  feet  in  thickness,  the  successive  beds  crowded  with 
organic  remains  and  revealing  the  historic  sequence  of  varying  organic 
types  as  the  life  responded  to  slight  changes  of  environment.  Here, 
as  at  countless  other  localities,  the  paleontologist  gets  a  view  of 


THE  PALEONTOLOGIC  RECORD  5 

changes,  of  movements,  of  trend  and  tendency  among  living  things 
ranging  over  a  period  of  time  equal  to  many  millenniums. 

Another  life  record  of  especial  interest,  typical  of  many  scattered 
up  and  down  the  land  areas  of  the  globe,  is  furnished  by  the  Osage 
division  of  the  Mississippian  at  Burlington  and  Keokuk.  Of  one  group 
of  crinoids,  the  Camerata,  these  Mississippian  limestones  have  yielded 
about  250  species,  and  of  other  groups  a  number  about  equally  as  great. 
The  beauty  and  perfection  of  the  individual  specimens  can  be  ap- 
preciated only  by  those  who  have  had  the  good  fortune  to  see  the  superb 
collections  of  Wachsmuth  and  Springer.  Crinoids  flourished  here  in 
such  numbers  that  beds  of  limestone  150  feet  in  thickness  are  built 
practically  of  crinoidal  remains  and  nothing  else.  The  time  repre- 
sented was  long  enough  to  allow  of  a  series  of  modifications  of  such  ex- 
tent that  the  crinoid  fauna  of  the  Upper  Burlington  is  very  distinct 
from  that  of  the  lower  beds  of  the  same  formation,  while  the  fauna  of 
the  Keokuk  differs  from  both.  Here  again  the  paleontologist  is 
favored,  not  only  with  a  wealth  of  material,  but  with  an  opportunity  to 
note  the  trend  and  tendency  of  things.  This  was  the  time  of  greatest 
development,  of  highest  prosperity,  among  camerate  crinoids.  But  in 
the  midst  of  this  prosperity  the  trained  paleontologist  may  discover 
signs  of  degeneration,  the  prophecy  of  speedy  extinction.  The  law 
enunciated  by  Beecher  and  quoted  by  Professor  Woodward  in  his  ad- 
dress before  the  geological  section  of  the  British  Association  at  its 
meeting  in  Winnipeg  last  summer,  is  well  exemplified  in  the  Missis- 
sippian history  of  this  particular  group  of  crinoids.  The  tendency 
among  any  division  of  skeletal-bearing  animals  to  run  to  extravagant 
ornamentation  in  the  way  of  ribs,  nodes,  spines  or  other  excesses  of 
dead,  useless,  skeletal  matter,  is  something  that  precedes  and  presages 
the  decline  and  death  of  the  race.  Even  in  the  Upper  Burlington  the 
skeleton  of  the  crinoids  is  heavier  than  in  the  Lower;  stronger  nodes 
on  the  plates  are  produced;  more  arm  plates  are  incorporated  in  the 
dorsal  cup;  the  animals  are  weighted  down  with  useless  matter.  This 
tendency  is  carried  to  extremes  in  the  Keokuk  limestone,  a  fact  well 
exemplified  by  the  species  figured  on  plate  15  of  Hall's  "  Geology  of 
Iowa,"  Volume  I.,  part  II.  In  these  species  the  development  of 
massive  spines  and  heavy  nodose  plates  reaches  its  maximum.  The 
race  has  come  to  the  end  of  its  career.  When  the  Keokuk  closes,  only  a 
few  of  the  simpler  forms  of  the  Camerata  survive,  and  even  these 
shortly  disappear.  The  paleontologist  sees  the  operation  of  the  same 
law,  the  same  trend  and  tendency,  among  the  Cretaceous  Ammonoids; 
in  many  other  groups  of  animals  it  is  as  clearly  manifest ;  but  it  would 
not  be  profitable,  before  such  a  body  as  this,  to  carry  the  discussion 
farther,  even  if  the  limits  of  the  paper  permitted.  Let  me  close  by 


6  THE  PALEONTOLOGIC  RECORD 

quoting  from  the  address  of  Professor  Woodward,  to  which  reference 
has  already  been  made : 

Geology  and  paleontology  in  the  past  have  furnished  some  of  the  grandest 
contributions  to  our  knowledge  of  the  world  of  life;  they  have  revealed  hidden 
meanings  which  no  study  of  the  existing  world  could  even  suggest;  and  they 
have  started  lines  of  inquiry  which  the  student  of  living  plants  and  animals 
alone  would  scarcely  have  suspected  to  be  profitable. 

ADEQUACY   OF   THE   PALEONTOLOGIC   KECOED 

BY  R.   S.  BASSLER 

U.    S.    NATIONAL   MUSEUM 

THE  imperfection  or  inadequacy,  instead  of  the  adequacy  of  the 
paleontologic  record,  has  long  been  a  favorite  subject  of  discus- 
sion, and  it  is  only  within  recent  years  that  this  heresy  of  an  imperfect 
record  is  being  abandoned  by  paleontologists  in  general.  However,  as 
many  of  our  biologic,  and  even  a  few  of  our  paleontologic,  friends  still 
have  doubts  regarding  the  matter,  the  present  conference  upon  this  and 
allied  subjects  is  very  opportune. 

I  have  a  vivid  recollection  of  the  joy  experienced  in  my  school  days, 
when,  during  an  examination  in  geology,  the  subject  of  an  impromptu 
essay  was  announced  as  "The  Imperfection  of  the  Paleontologic 
Kecord."  Here  was  a  subject  in  which  I  was  well  grounded  from  text- 
book reading,  and  I  remember  distinctly  the  telling  points  made.  The 
lack  of  hard  parts  causing  the  absence  of  many  classes  of  animals ;  the 
great  amount  of  unrepresented  time  in  the  geologic  column;  the  meta- 
morphism  and  consequent  disappearance  of  fossils,  and,  when  present, 
the  frequent  imperfectness  of  the  specimens  themselves,  were  dwelt  on 
in  great  detail.  Since  that  time,  my  experience  in  invertebrate  paleon- 
tology has  compelled  me  to  unlearn  every  one  of  these  supposed  facts, 
and  to  come  to  the  conclusion  that,  considered  both  biologically  and 
stratigraphically,  the  paleontologic  record  is  sufficiently  adequate  for 
all  reasonable  purposes. 

Professor  Calvin's  paper  tells  us  (1)  of  the  detailed  perfection  of 
the  record,  (2)  of  the  profusion  of  the  material,  and  (3)  of  the  broad 
view  as  to  trend  and  tendency  of  biologic  characters  which  the  study 
of  paleontology  gives.  His  presentation  of  the  subject  is  such  that  we 
must  all  agree  with  him.  It  therefore  seems  best  for  me  to  confine  my 
remarks  to  the  reasons  usually  advocated  for  the  imperfection,  namely, 
the  lack  of  hard  parts  in  many  animals,  metamorphism,  the  frequent 
imperfect  preservation  of  fossils,  and  the  unrepresented  time  in  the 
geologic  column. 

The  lack  of  hard  parts  in  many  animals  is  a  serious,  although  not 
fatal,  objection  to  their  preservation  as  fossils.  For  the  best  results  as 


THE  PALEONTOLOGIC  RECORD  7 

fossils,  a  stony  framework  of  some  kind  is  desirable,  as  we  all  know, 
but  horny,  or  even  the  most  perishable  materials  may  be  preserved  under 
favorable  conditions.  Mr.  Walcott's  work  on  the  Medusas,  and  the 
researches  of  Euedemann  on  the  graptolites,  as  well  as  the  work  of 
others  whom  we  can  call  to  mind,  are  examples  of  excellent  results  from 
material  of  the  latter  nature,  not  to  mention  the  hairs  of  the  worm  so 
carefully  described  by  the  Cincinnati  paleontologist! 

The  metamorphism  and  apparently  complete  obliteration  of  all 
fossil  remains  in  the  rocks  of  certain  large  areas  is  likewise  an  appar- 
ently serious  objection  to  the  adequacy  of  the  record,  but  here  careful 
searching  with  the  structural  relations  in  mind  will  reveal  the  fossils, 
if  present  at  all.  The  greatly  folded  and  cleaved  slates,  schists  and 
volcanic  tuffs  of  the  Piedmont  area  have  long  been  the  despair  of  both 
paleontologist  and  geologist,  but  at  this  meeting  of  the  Geological 
Society  of  America,  the  State  Geologist  of  Virginia  will  tell  of  Cin- 
cinnatian  fossils  in  the  so-called  Algonkian  and  other  schists  and  vol- 
canics  of  the  easternmost  Piedmont  of  that  state.  In  this  case  the  dis- 
covery of  well-preserved  fossils  was  quite  simple.  It  consisted  merely 
in  finding  a  place  where  the  cleavage  and  stratification  coincided,  and 
then  working  hard. 

Professor  Calvin  has  spoken  of  the  richness  and  beautiful  preserva- 
tion of  certain  Paleozoic  faunas.  While  the  beauty  and  occasional 
richness  of  such  faunas  is  not  to  be  gainsaid,  we  must  not  forget  the 
many  horizons  and  localities  affording,  in  comparison,  specimens  so 
poorly  preserved  that  they  might  readily  furnish  an  argument  for  the 
inadequacy  of  the  record.  Nor  must  we  forget  that  in  quite  a  portion 
of  the  geologic  column  organic  remains  are  not  only  poorly  preserved, 
but  are,  as  known  at  present,  very  rare.  However,  these  lean  spots  can 
be  made  most  productive  of  paleontologic  results  by  careful  search  and 
by  methods  of  preparation.  Several  years  ago  the  number  of  lower 
Paleozoic  fossils  found  in  the  Ozarks  could  almost  be  counted  on  one's 
fingers,  but  we  now  have  in  the  National  Museum,  from  this  formerly 
almost  barren  spot,  several  hundred  drawers  of  beautiful  material. 

Fortunately  the  preparation  and  methods  of  study  of  paleontologic 
material  has  progressed  to  such  a  point  that  a  poor  fossil  is  no  longer  a 
bugbear.  A  specimen  may  be  considered  inadequate  for  study  because 
it  is  covered  with  refractory  clay.  The  application  of  caustic  potash 
solves  this  difficulty.  Certain  limestone  bands  in  the  New  York 
Niagaran  and  Cayugan  are  crowded  with  fossils,  although  often  few  of 
the  species  can  be  determined  because  of  a  hard,  clayey  covering.  In 
preparing  some  specimens  for  exhibition,  the  treatment  with  caustic  of 
a  single  slab,  about  three  inches  wide  and  five  inches  long,  enabled  me 
to  bring  out  over  a  hundred  species  on  one  surface  alone,  not  including 
the  ostracods  and  other  microscopic  organisms.  How  often  will  the 
present  sea  bottom  furnish  such  results? 


8  THE  PALEONTOLOGIC  RECORD 

Nature  is  very  kind  in  preparing  fossils  for  us.  The  Onondaga 
limestone,  at  the  Falls  of  the  Ohio,  although  only  a  few  feet  in  thick- 
ness, has  yielded  seven  hundred  or  more  species  of  exquisitely  preserved 
fossils.  Examine  the  freshly  quarried  limestone  and  you  may  be  able 
to  crack  out  perhaps  two  dozen  species  of  poorly  preserved  material, 
but  go  to  the  neighboring  field  where  solution  of  the  limestone  and 
silicification  of  its  contained  fossils  has  occurred,  and  a  host  of  beautiful 
forms  awaits  you.  Strata,  which  under  ordinary  circumstances  would 
yield  very  poor  fossils,  can,  if  silicification  has  commenced,  be  made  to 
afford  excellent  specimens.  By  exposure  to  the  weather  for  a  year  or 
so,  the  silicification  can  be  advanced  to  such  a  stage  that  etching  with 
acid  will  free  the  fossils.  The  beautiful  etched  material  from  the 
New  Scotland  of  New  York  is  a  familiar  example  of  this  style  of 
preparatory  work.  Most  of  the  Cambrian  and  Ordovician  formations 
of  the  Appalachian  Valley  yield  shells  which,  as  they  occur  in  the  lime- 
stone, are  almost  impossible  as  subjects  for  study,  but  as  silicified 
pseudomorphs,  all  the  beauty  and  detail  of  the  original  shell  are 
reproduced. 

Thin  sections  are  a  valuable  aid  in  identifying  the  merest  fragment 
of  certain  classes  of  organisms,  and  their  use  here  is  indispensable. 
A  thin  section  of  an  otherwise  undeterminable  fragment  of  a  Cambrian 
protremate  brachiopod  will  distinguish  the  horizon.  Other  methods  of 
preparation  and  study  might  be  mentioned,  but  time  forbids,  although 
I  can  not  refrain  from  speaking  of  the  several  whitening  processes. 
The  use  of  a  coating  of  ammonium  chloride  or  anilin  chloride  on  fossils 
for  photographic  purposes  is  well  known,  but  the  excellent  results 
obtained  from  the  use  of  the  same  process  in  the  study  of  poor  material 
may  not  be  so  apparent  to  all.  A  trilobite  indistinctly  outlined  in  the 
rock  under  ordinary  circumstances,  flashes  into  bold  relief  when  covered 
with  the  ivory  white  film  of  ammonium  chloride.  Casts  and  molds  of 
fossils  too  indistinct  to  show  any  structure  ordinarily,  will  reveal  many 
characters  when  so  whitened.  Recently  occasion  arose  to  study  a 
species  of  Cambrian  phyllopod  which  had  already  been  described  and 
figured.  The  specimen  was  practically  nothing  but  a  film  upon  the 
rock,  and  apparently  the  last  word  had  been  said  upon  it.  It  was  sug- 
gested that  the  specimen  be  whitened  and  then  photographed  with  the 
sun's  rays  nearly  parallel  to  its  surface.  The  result  was  most  gratifying 
as  structures  which  could  not  be  proved  to  exist  by  the  aid  of  the  eye 
alone,  came  into  plain  view  in  the  negative.  All  these  various  methods 
of  preparation  and  study  make  available  a  vast  amount  of  material 
which  formerly  was  thought  too  imperfect  to  be  fully  considered  in 
determining  the  adequacy  of  the  record,  hence  the  great  value  of  such 
methods  to  the  paleontologist  is  obvious. 

The  real  adequacy  of  the  record,  if  it  might  be  so  called,  lies  in  the 


THE  PALEONTOLOGIC  RECORD  9 

imperfections  or  gaps  in  the  stratigraphic  column.  Measured  accord- 
ing to  the  sections  of  twenty-five  years  ago,  the  number  of  these  gaps  is 
growing  greater  and  greater,  yet  with  the  discovery  and  intercalation 
of  new  formations,  the  aggregate  of  which  at  the  present  day  has  almost 
doubled  the  thickness  of  Paleozoic  rocks  in  the  last  decade,  manifestly 
the  great  breaks  are  being  reduced.  It  was  not  so  many  years  ago  that 
the  Potsdam  sandstone  was  supposed  to  be  the  oldest  fossiliferous  sedi- 
mentary rock,  yet  now  we  know  that  many  thousands  of  feet  of  much 
more  highly  fossiliferous  strata  intervene  between  this  formation  and 
the  Azoic,  and  that  other  thousands  occur  above  the  Potsdam  and 
below  the  Ordovician  as  then  recognized. 

With  the  intercalation  of  new  formations  and  the  consequent 
diminution  in  the  size  of  the  stratigraphic  gaps,  it  is  then  probably 
only  a  matter  of  time  before  the  complete  faunal  succession  can  be 
established.  The  break  in  stratigraphy  at  one  point  will  be  bridged 
over  in  another  area,  and  it  is  possible  that  in  only  a  few  regions,  such 
as  on  the  borders  of  the  continent,  will  permanent  gaps  exist.  Faunas 
are  and  will  be  traced  from  one  area  to  another  until  in  time  we  shall 
know  their  complete  geologic  history.  With  these  data  in  hand,  the 
study  of  their  correlation  will  not  only  be  greatly  simplified,  but  also 
will  not  be  hampered  by  time  breaks  in  the  record.  While  imperfect, 
or  possibly  irretrievably  lost  at  the  dawn,  the  faunas  of  succeeding  times 
are  ample  for  all  purposes. 

INTEKDEPENDENCE  OF  STEATIGEAPHY  AND 
PALEONTOLOGY 

BY  DB.  W.  J.  SINCLAIR 

PRINCETON    UNIVERSITY 

IN  discussing  this  subject  from  the  view-point  of  a  vertebrate  paleon- 
tologist, I  am  disposed  to  lay  stress  on  what  I  believe  ought  to  be, 
rather  than  what  has  been,  the  degree  of  interdependence  of  these  two 
branches  of  geology.  Vertebrate  paleontology  has  been  studied  very 
largely  from  the  morphological  and  genealogical  side,  a  study  of  struc- 
ture, adaptation  and  the  evolution  of  phyla.  Stratigraphic  geology  has 
been  invoked  only  when  it  became  necessary  to  know  the  order  of  super- 
position of  the  various  horizons,  to  determine  the  true  evolutionary 
succession  of  a  phylum  or  development  of  an  adaptation. 

I  have  purposely  presented  this  extreme  view,  not  because  I  believe 
that  such  studies  may  not  be  classed  legitimately  as  paleontological,  but 
because  I  wish  to  emphasize,  by  contrast,  the  view-point  which  we 
should  ever  keep  before  us  as  paleontologists — the  use  of  our  materials 
as  Leitfossilien.  The  two  correlative  conceptions  of  the  faunal  unit 
and  the  zone,  a  more  or  less  restricted  association  of  animals  and  the 


io  THE  PALEONTOLOGIC  RECORD 

rock  layer  in  which  it  occurs  and  which  it  characterizes,  long  and  suc- 
cessfully employed  by  the  invertebrate  paleontologist,  must  be  recog- 
nized and  used  by  us  also. 

I  need  hardly  refer  to  the  fact  that  the  determination  of  the  geolog- 
ical age  and  the  successful  correlation  of  many  North  American  forma- 
tions, ranging  from  Mesozoic  to  Pleistocene,  depend  in  large  measure,  if 
not  entirely,  on  vertebrate  fossils.  I  need  only  contrast  the  American 
series  of  Pleistocene  glacial  and  interglacial  stages,  determinable  at 
present  only  by  the  strictly  stratigraphic  method  of  superposition,  with 
the  carefully  worked-out  series  in  Europe,  where  each  epoch  of  ice 
advance  and  retreat  is  characterized  by  its  particular  fauna  and  flora. 
That  even  the  beginnings  of  stratigraphic  paleontology,  as  contrasted 
with  the  morphological,  will  lead  to  immediate  and  valuable  results,  is 
strikingly  shown  by  Professor  Calvin's1  recent  paper  in  the  Bulletin 
of  our  parent  society,  the  Geological  Society,  in  which  he  describes  the 
Aftonian  mammal  fauna  from  the  earliest  of  American  interglacial 


While  readily  admitting  that  the  slow-moving  invertebrate,  living, 
it  may  be,  in  the  very  mud  which  is  destined  to  become  the  matrix  of 
its  fossil  remains,  enjoys  advantages  as  a  prospective  horizon-deter- 
miner which  the  agile  vertebrate  can  more  readily,  and  does  most  will- 
ingly, escape,  still  the  short  life  of  vertebrate  species,  and  their  com- 
paratively rapid  evolution,  fit  them  for  use  as  index  fossils  quite 
admirably.  The  localization  of  mammalian  faunas,  their  inability  to 
cross  barriers  such  as  ocean  basins  and  great  mountain  ranges,  their 
dependence  on  temperature,  etc.,  are  comparable  to  similar  conditions 
circumscribing  the  free  migration  of  invertebrates.  We  should  not 
expect  to  find  in  the  distribution  of  vertebrate  faunas  the  analogues  of 
the  cosmopolitan  graptolite  zones  of  the  Ordovician  or  the  ammonite 
zones  of  the  Trias,  but  we  can  work  out  our  major  zones  as  recognized 
by  the  great  migrational  movements  among  vertebrates,  expressed  in 
changes  in  the  faunas  and  the  rock  succession,  which  will  give  us  a 
world  scale,  and  then,  by  interpolation,  fill  in  the  minor  and  local  sub- 
divisions which  we  probably  shall  not  be  able  to  correlate  at  once,  but 
which  there  is  every  reason  to  believe  we  may  be  able  to  do  later. 

The  attempt  will  be  accompanied  by  difficulties  which  are  not  appre- 
ciated by  the  invertebrate  paleontologist,  and  I  speak  feelingly  and  from 
experience,  for  there  is  a  difference  between  collecting,  on  the  one  hand, 
from  a  layer  a  few  inches  thick,  crowded  with  shells,  and,  on  the  other, 
tramping  miles  up  hill  and  down  over  beds  hundreds  of  feet  thick,  to 
be  rewarded  by  a  few  teeth,  a  lot  of  useless  bone  fragments  or  nothing. 
Horizons  based  on  vertebrates  must  include  larger  stratigraphic  units 

1  Bulletin  of  the  Geological  Society  of  America,  Vol.  20,  pp.  341-356,  Pis. 
16-27,  October,  1909. 


THE  PALEONTOLOGIC  RECORD  n 

than  are  recognized  for  invertebrates,  because  of  the  scattered  nature  of 
the  material  and  the  additional  probability  that  continental  deposits,  in 
which  alone  vertebrates  have  their  chief  importance  as  guide  fossils, 
have  accumulated  more  rapidly  than  marine  beds.  Similarly,  condi- 
tions peculiar  to  their  mode  of  deposition  make  it  difficult,  perhaps 
impossible,  to  define  lithologically  the  limits  of  the  zones  we  are  at- 
tempting to  characterize.  And  here  another  trouble  confronts  us,  for 
the  faunas  are  incompletely  known,  and  we  are  not  yet  in  a  position  to 
dogmatize  too  freely  on  the  subject  of  vertebrate  index  fossils.  But 
that  the  method  of  zonal  studies  is  the  correct  one  is  very  clearly  shown 
in  Dr.  Matthew's2  recent  monograph  on  the  Carnivora  and  Insectivora 
of  the  Bridger  Eocene,  and  will  be  demonstrated  with  equal  force  when 
Professor  Osborn's  volume  on  the  titanotheres  is  published. 

Various  attempts  have  been  made  at  the  correlation  of  European 
and  American  mammal  horizons,  their  measure  of  success  depending 
entirely  on  the  degree  of  closeness  with  which  these  correspond  to 
true  zones.  At  present,  we  are  attempting  to  correlate  subdivisions, 
both  faunal  and  stratigraphic,  of  all  orders  of  magnitude,  the  majority 
including  many  faunules  and  many  zones.  Evidently,  this  tendency 
must  be  corrected  by  careful  zonal  studies,  if  vertebrate  paleontology 
is  to  have  any  standing  as  an  aid  to  stratigraphy  in  the  correlation  of 
our  non-marine  formations. 

BIOLOGIC   PRINCIPLES   OF  P ALE 0 GEOGRAPHY 

BY  PBOFESSOR  CHARLES  SCHUCHERT 

YALE    UNIVERSITY 

IN"  deciphering  the  ancient  geography  as  to  the  position  of  the  marine 
waters  and  the  land  masses,  we  as  pioneers  in  this  work  must  be 
controlled  primarily  by  the  known  fossilized  life  and  secondarily  by 
the  character  and  place  of  deposition  of  the  geologic  formations.  This 
record  is  most  extensive  and  best  preserved  in  the  deposits  of  the  con- 
tinental and  the  littoral  region  along  the  continental  shelves  of  the 
oceanic  areas.  Back  of  these  two  principles,  however,  there  is  another 
that  eventually  will  become  the  primary  guiding  factor.  It  is  the  prin- 
ciple of  diastrophism — one  seeking  to  explain  the  causes  for  the 
periodic  movements  of  the  lithosphere. 

In  our  study  of  the  ancient  seas  with  their  sediments  and  entombed 
life  we  have  safe  guidance  in  the  phenomena  of  the  present.  Ludwig 
in  1886  estimated  the  species  of  animals  then  known  to  naturalists  as 
upwards  of  312,000,  and  in  1905  Stiles  thought  this  great  total  had 
increased  to  about  470,000  forms.  Of  this  sum  fully  60  per  cent,  are 
insects,  and  of  the  remainder,  the  writer  concludes  that  about  25  per 
a  Memoirs  American  Museum  of  Natural  History,  Vol.  IX.,  Part  VI.,  1909. 


12  THE  PALEONTOLOGIC  RECORD 

cent.,  or  115,000  species,  live  in  the  sea,  and  71,000  have  their  habitat 
on  the  land  or  in  the  waters  of  the  land.  Of  the  115,000  kinds  of 
known  animals  inhabiting  the  seas  nearly  70  per  cent,  are  Ccelenterata, 
Echinodermata,  Molluscoidea  and  Mollusca,  the  types  of  organisms 
most  often  found  by  the  stratigrapher  and  on  which  he  is  largely  de- 
pendent in  deciphering  the  ancient  geography. 

Let  us  now  examine  into  the  number  of  available  fossil  forms  made 
known  by  the  paleontologists.  As  early  as  1868,  Bigsby  in  his 
"Thesaurus  Siluricus "  listed  8,897  species  from  the  strata  beneath 
the  Devonic,  and  in  his  "  Thesaurus  Devonico-Carbouiferous "  of 
1878,  he  further  enumerated  about  5,600  Devonic  and  8,700  Carbonic 
forms.  In  1889  Neumayr  concluded  that  there  were  then  known  about 
10,000  Jurassic  species.  We  may  therefore  estimate  that  the  paleontol- 
ogists of  to-day  have  access  to  at  least  100,000  species  of  fossils.  Their 
numbers  in  the  geologic  scale  are  about  as  follows:  Cambric  2,000, 
Ordovicic  8,000,  Siluric  8,000,  Devonic  9,000,  Lower  Carbonic  7,000, 
Upper  Carbonic  8,000,  Permic  4,000,  Triassic  6,000,  Jurassic  15,000, 
Cretacic  10,000  and  Tertiary  25,000.  The  end  of  species-making  is 
not  at  all  in  sight,  and  the  day  will  come  when  paleontologists  will  deal 
with  ten  times  as  many  species  as  are  now  known. 

Stiles  tells  us  that  zoologists  know  but  from  10  to  20  per  cent,  of 
the  living  forms,  and  there  should  therefore  be  from  3,760,000  to 
4,700,000  different  kinds  of  animals  alive  to-day,  ranging  from  the 
protozoa  to  man.  Now  let  us  compare  the  abundance  of  living  ani- 
mals with  those  of  the  geologic  ages,  and  especially  with  the  Jurassic 
period,  of  which  life  we  have  probably  a  better  knowledge  than  of  any 
time  back  of  the  Tertiary.  The  European  Jurassic  has  long  been 
divided  into  33  zones  (Buckman  hints  at  a  probable  100),  and  if  we 
hold  that  each  one  of  these  times  had  only  one  quarter  as  many  species 
as  in  the  lowest  estimate  of  the  present  world,  there  must  have  lived 
during  the  entire  Jurassic  something  like  31,000,000  kinds  of  animals. 
Yet  paleontologists  have  described  not  more  than  15,000  Jurassic 
forms.  The  great  imperfection  of  the  extinct  life  record  is  thus  forcibly 
brought  to  our  attention,  and  we  learn  from  these  estimates  that  for 
each  krnd  of  animal  preserved  in  the  rocks  more  than  2,000  other  kinds 
are  utterly  blotted  out  of  the  geologic  record. 

Much  of  this  more  apparent  than  real  imperfection,  however,  is 
due  to  the  vast  number  of  insect  species  now  living — animals  that  must 
have  been  comparatively  few  in  the  Jurassic,  due  in  the  main  to  the 
absence  of  flowering  plants.  From  these  figures,  however,  we  must  not 
conclude  that  the  geologic  record  is  equally  imperfect  throughout;  for 
the  paleontologist  studying  marine  fossils  well  knows  that  he  can  not, 
as  a  rule,  hope  to  study  other  than  those  kinds  of  animals  that  have 
hard  and  calcareous  or  siliceous  external  or  internal  skeletons.  Of 


THE  PALEONTOLOGIC  RECORD  13 

such  there  may  be  in  the  present  seas  about  250,000  kinds,  of  which 
about  25,000  have  been  named.  Therefore  on  this  basis  we  can  say 
that  the  student  of  Jurassic  faunas  knows  1  species  in  every  54  of 
shelled  animals  that  lived  during  this  period. 

This  admittedly  great  imperfection  of  the  life  record  needs  to  be 
further  explained  so  that  the  reader  will  not  arrive  at  the  erroneous 
conclusion  that  modern  stratigraphy  rests  upon  very  insecure  founda- 
tions. The  stratigrapher  in  determining  the  age  of  a  given  deposit, 
and  in  the  identification  of  it  from  place  to  place  and  from  country  to 
country,  and  even  across  the  great  oceans,  deals  in  his  work  not  with 
quantity  of  species,  but  with  comparatively  small  numbers  of  con- 
stantly recurring  hard  parts  of  certain  species  that  are  more  often  of 
marine  than  of  land  origin.  Many  of  these  forms  have  but  local  value 
but  others  have  spread  thousands  of  miles,  and  some  of  the  long  en- 
during species  range  over  the  greater  part  of  the  earth.  Some  of  the 
best  guide  fossils  in  the  Paleozoic  are  the  brachiopods  because  they 
are  present  in  nearly  all  the  strata  of  this  era.  The  writer  in  1897 
listed  1,859  forms  then  known  from  these  rocks  of  North  America. 
Of  these  about  28  per  cent.,  or  537  species,  had  great  geographic  dis- 
tribution. 117  species  are  found  in  the  Rocky  Mountain  area,  the 
Mississippi  valley  and  the  Appalachian  region,  and  of  these  36  are  also 
known  to  occur  in  foreign  countries.  The  number  of  species  common 
to  North  America  and  other  continents,  however,  is  121.  It  is  upon 
faunal  assemblages  of  this  quantity  and  nature  that  the  stratigrapher 
relies  most  in  deciphering  the  former  extent  of  the  continental  seas. 

In  the  making  of  paleogeographic  maps  or  in  the  determination  of 
geologic  time,  using  fossils  as  the  essential  basis,  we  have  guidance  in 
those  of  marine  faunas,  and  the  floras  and  faunas  of  the  land  and  its 
fresh  waters.  Of  these  widely  differing  realms  or  habitats  we  now 
know  that  the  fossils  of  the  marine  faunas  are  the  more  reliable  not 
only  because  there  are  so  many  more  of  them  than  of  the  land  dwellers, 
but  more  especially  because  their  geologic  succession  is  far  more  com- 
plete. The  conditions  of  preservation,  that  is,  appropriate  burial  in 
sediments,  are  always  at  hand  in  marine  waters,  but  on  the  land  en- 
tombment occurs  only  exceptionally,  whereas  the  life  of  fresh  waters 
is  very  meager  and  almost  unchanging  during  geologic  time.  Then, 
too,  marine  life  is  "less  affected  by  meteorologic  factors,  and  more 
dependent  upon  conditions  which  affect  the  whole  hydrosphere  rather 
than  small  areas  of  it.  The  struggle  for  life  is  less  intense,  the  food 
supply  generally  more  adequate,  enemies  less  vigorous,  and  dangerous 
fluctuations  of  temperature  far  less  frequent,  in  the  sea  than  on  land. 
The  same  features  make  the  land  fauna  more  clearly  indicative  of 
minor  divisions  of  the  scale,  and  of  the  progress  of  organic  evolution 


i4  THE  PALEONTOLOGIC  RECORD 

in  the  general  region  concerned;  while  less  conclusive  as  to  the  con- 
temporaneity of  widely  separated  though  analogous  faunas."1 

In  regard  to  the  probable  geographic  position  of  the  shore  lines  we 
rarely  have  safe  guidance  in  the  fossils,  and  for  this  depend  on  the 
nature  of  the  deposits.  Greatest  dependence  is  placed  upon  the  geo- 
graphic position  of  sandstones  and  especially  on  conglomerates  to  indi- 
cate the  probable  former  shores.  Limestones  of  uniform  character 
and  wide  distribution  are  indicative  of  greater  distance  from  land. 
Shallowness  of  the  continental  seas  is  proved  by  a  rapid  change  in 
the  character  of  the  sediments  both  laterally  and  vertically,  and  by 
the  oolite  and  dolomite  deposits.  Intraformational  conglomerates, 
coral  reefs,  ripple  marks,  and  shrinkage  cracking  furnish  further  evi- 
dence to  the  same  conclusion.  Storm  waves  are  known  to  plough  the 
present  sea-bottom  to  depths  of  160  feet.  Calcareous  muds  are  now 
forming  in  tropical  and  subtropical  waters  at  sea-level  around  coral 
reefs,  and  elsewhere  in  these  latitudes  at  depths  from  200  to  600 
meters.  It  is  probable  that  all  of  the  ancient  great  limestone  deposits 
are  of  warm  waters,  and,  if  so,  are  an  additional  aid  in  discerning  the 
geologic  times  and  regions  of  milder  climates. 

Phosphatic  concretions  form  in  the  littoral  region  where  the  tem- 
perature changes  are  rapid,  as  off  the  coast  of  the  New  England  states, 
and  periodically  cause  much  destruction  of  the  individual  life.  The 
carcasses  decompose  at  the  bottom  of  the  sea,  making  nuclei  for  the 
accretion  of  phosphate  of  lime,  and  because  of  the  irregular  periodicity 
of  accumulation  come  to  be  arranged  in  definite  stratigraphic  zones. 
Old  Eed  sandstone  fishes  are  also  usually  found  in  clay  nodules  but 
abundantly  only  in  limited  zones  (Scaumenac,  Canada  and  Wildungen, 
Germany).  Have  these  also  been  killed  by  rapid  changes  in  the  tem- 
perature of  these  waters  ?  In  any  event  the  fish-bearing  beds  are  always 
found  near  the  shore  lines  of  Devonic  seas. 

Scour  of  sea  bottom  is  met  with  in  the  present  seas  where  great 
streams  of  water  are  forced  through  narrow  passages,  as  the  Gulf 
Stream  in  the  Meridian  area;  or  where  such  streams  impinge  against 
the  continental  shelf,  as  north  of  Cape  Hatteras,  or  flow  across  sub- 
merged barriers  "  a  few  miles  broad,"  as  the  Wyville-Thomson  ridge 
connecting  the  British  and  Faeroese  plateaus  (Johnstone,  1908,  31). 
Strong  currents  preventing  sedimentation  also  occur  in  long  and  narrow 
bays,  as  that  of  Fundy,  where  the  undertow  caused  by  the  very  high 
tides  of  this  region  sweeps  the  bottom  clean.  These  exceptional  and, 
after  all  is  said,  rather  local  occurrences  can  not  be  the  explanation  for 
the  many  known  breaks  in  the  geological  sedimentary  record,  the  dis- 
conformities  of  stratigraphers.  These  breaks  are  at  times  as  extensive 
as  the  North  American  continent  (post  Utica  break),  and  are  usually 

1  Ball,  Jour.  GeoL,  1909,  494. 


THE  PALEONTOLOGIC  RECORD  15 

of  very  wide  extent.  Scour  of  the  bottom  by  the  currents  of  the  an- 
cient continental  seas  will  not  explain  away  the  presence  of  these  truly 
land  times,  but  it  is  to  be  sought  in  the  oscillatory  nature  of  the  seas 
of  all  time  which  is  probably  caused  by  the  periodic  unrest  of  the 
earth's  crust  due  to  earth  shrinkage.  We  agree  with  Suess  that  "  Every 
grain  of  sand  which  sinks  to  the  bottom  of  the  sea  expels,  to  however 
trifling  a  degree,  the  ocean  from  its  bed,"  and  every  movement  of  the 
sea-bottoms  and  the  periodic  down  fracturing  of  the  horsts  causes  the 
strand  lines  to  tremble  in  and  out,  be  they  of  a  positive  or  transgres- 
sive  or  of  a  negative  or  land-making  character. 

The  ancient  marine  life  had  similar  zoogeographic  arrangement  to 
that  of  the  present.  It  can  be  grouped  into  local  faunas  and  these 
combined  into  subprovinces,  provinces  and  realms.  Their  distribution 
is  governed  primarily  by  the  presence  or  absence  of  land  barriers,  and 
secondarily  by  temperature  and  latitude.  In  the  present  seas  tempera- 
ture is  one  of  the  main  factors  controlling  the  distribution  of  the 
species,  but  during  the  geologic  ages  the  climate  was,  as  a  rule,  far  more 
uniform  than  now,  as  we  are  living  under  the  influence  of  polar  ice 
caps  and  a  passing  glacial  period,  or  possibly  even  an  Interglacial 
period. 

The  faunas  with  which  the  stratigraphic  paleontologist  works  appear 
in  many  instances  as  suddenly  introduced  biotas.  Our  collaborators 
of  half  a  century  ago  explained  them  as  Special  Creations,  but  since 
their  time  we  have  learned  that  the  suddenly  appearing  faunas  are  not 
such  in  reality  but  only  seem  to  appear  rather  quickly  due  to  the  slow- 
ness of  sedimentary  accumulation.  Ulrich  estimates  that  the  American 
Paleozoic  has  less  than  100  mapable  units  or  formations,  each  with  a 
duration  of  probably  not  less  than  175,000  years.  Accordingly,  each 
foot  of  average  sedimentary  rock  has  taken  not  less  than  833  years  to 
accumulate.  Our  knowledge  regarding  the  average  rate  of  sedimentary 
marine  accumulation  is,  however,  as  yet  very  insecure,  and  to  make 
this  clear  some  of  the  remarks  made  by  Sollas,  President  of  the  Geo- 
logical Society  of  London  (1910),  will  be  quoted.  He  was  led  to  make 
these  remarks  after  the  reading  of  a  paper  by  Buckman  correlating 
the  Jurassic  sections  of  South  Dorset.  He  said,  "  The  correlation  of 
thin  seams  with  thick  deposits  was  a  matter  of  great  importance.  .  .  . 
It  might  afford  some  hints  as  to  the  order  of  magnitude  of  the  scale  of 
time.  If  we  assumed  that  one  foot  of  sediment  might  accumulate  in 
a  century,  in  an  area  of  maximum  deposition,  then  in  the  case  of  the 
seam  two  inches  thick,  which  was  represented  by  250  feet  in  the  Cottes- 
wolds,  the  rate  of  formation  would  be  less  probably  than  1  foot  in 
150,000  years."  What  Ulrich's  estimate  of  time  necessary  for  the 
accumulation  of  one  foot  of  average  sediment  means  to  migratory  faunas 
may  be  illustrated  by  the  spreading  of  Littorina  littorea.  In  the  last 


THE  PALEONTOLOGIC  RECORD 

century  this  edible  European  gastropod  was  introduced  at  Halifax, 
Nova  Scotia,  and  in  50  years  attained  the  Delaware  Bay  and  north  to 
Labrador.  Taking  this  dispersion  as  the  basis  for  calculating  f aunal  mi- 
grations, we  learn  that  they  may  spread  500  miles,  while  one  sixteenth 
of  an  inch  of  average  sediment  is  depositing,  or  8,000  miles  during 
the  time  of  one  foot  of  sedimentary  accumulation.  If,  therefore,  Paleo- 
zoic faunas  migrated  "  only  one  fiftieth  as  fast  as  this  living  shell,  then 
we  may  reasonably  assert  essential  contemporaneity  for  stratigraphic 
correlations  extending  entirely  across  the  continent."  We  have  here 
an  explanation  for  the  apparently  sudden  distribution  of  the  Ordovicic 
brachipod  Rhynchotrema  capax,  that  everywhere  holds  an  identical 
geologic  horizon  from  Anticosti  to  the  Big  Horns  and  from  El  Paso, 
Texas,  to  Arctic  Alaska.  Spirifer  hungerfordi  spreads  during  the  first 
half  of  Upper  Devonic  time  from  the  Urals  to  Iowa,  and  another 
brachiopod,  String ocephalus  burtoni,  migrates  during  the  last  third  of 
Middle  Devonic  time  from  western  Europe  to  Manitoba. 

The  life  of  the  present  seas  extends  from  the  strand-line  to  the 
deepest  abj^ss,  but  by|£ar  the  greatest  quantity  and  variety  lives  in  the 
upper  sunlight,  photic  or  diaphanous  region.  Photographically  the 
light  of  the  sun  is  detectable  in  exceptionally  clear-water  tropical  seas 
to  a  depth  of  about  2,000  feet,  but  Johnstone  places  the  average  depth 
for  all  waters  at  650  feet,  beyond  which  there  is  more  or  less  of  total 
darkness,  the  aphotic  realm. 

Sunlight  is  the  first  essential  for  the  existence  of  life.  Where  it 
penetrates,  there  plant  life  is  possible,  and  this  life  is  the  substratum 
on  which  all  animal  life  is  ultimately  dependent  for  food.  Near  the 
surface  of  the  sea  lives  the  plankton,  sometimes  referred  to  as  the 
"pastures  of  the  sea"  and  compared  with  the  "grass  of  the  fields." 
Most  of  this  plankton  consists  of  diatoms  that  at  present  are  by  far 
more  prolific  in  the  cooler  polar  waters.  At  times  of  greatest  abun- 
dance in  Kiel  Bay  as  many  as  200  of  these  "  jewels  of  the  plant  world  " 
are  contained  in  a  drop  of  water,  and  in  the  Antarctic  seas  there  is 
an  area  of  ten  and  one  half  million  square  miles  where  diatom  ooze  is 
accumulating.  They  are  the  principal  food  supply  for  most  of  the  ses- 
sile benthos,  or  bottom  life,  among  which  the  mollusca  and  brachiopods 
are  of  the  greatest  importance  in  paleogeography. 

Geologic  deposits  rich  in  diatoms  are  sometimes  regarded  as  those 
of  the  deep  sea,  at  least  as  of  deeper  waters  than  those  of  continental 
seas.  The  English  Carbonic  deposits,  rich  in  diatoms,  have  a  fauna 
whose  species  are  all  of  the  shallow  water  kinds.  The  vast  Miocene 
diatom  deposits  of  California,  described  by  Arnold,  have  living  bottom 
types  of  foraminifera  that,  according  to  Bagg,  do  not  indicate  a  depth 
of  over  500  fathoms. 

From  the  present  distribution  of  marine  life  we  learn  that  the 


THE  PALEONTOLOGIC  RECORD  17 

greatest  bulk  of  invertebrates  are  restricted  to  the  bottom  of  the  shal- 
low seas  within  the  depth  to  which  sunlight  readily  penetrates,  that  is, 
a  depth  on  the  average  not  over  600  feet.  The  value  of  this  observa- 
tion to  the  paleogeographer  and  the  student  of  fossil  marine  life  lies 
in  the  confirmation  of  paleontologists  that  continental  seas  are  shallow 
seas,  to  the  bottom  of  which  in  most  places  sunlight  permeates.  These 
seas  are  to  be  compared  with  the  littoral  regions  of  the  present  oceans, 
and  they  are  the  areas  that  are  most  exposed  to  climatic  and  physical 
changes,  due  to  their  proximity  to  the  atmosphere  and  the  lands.  The 
life  of  these  waters  is,  therefore,  subject  to  an  environment  that  is 
more  or  less  changeable,  and  one  of  the  basic  causes  underlying  or- 
ganic change.  It  is  the  invertebrates  of  the  littoral  and  shallow  seas 
that  the  paleontologist  studies. 

In  the  tropical  and  subtropical  shallow  seas  one  meets  with  the 
greatest  variety  of  life  and  with  the  brighter  colored  and  more  orna- 
mental shelled  animals,  but  we  are  much  surprised  when  told  that  the 
greatest  number  of  individuals  occur  in  the  colder  shallow  waters  of 
the  temperate  and  polar  regions.  Johnstone  states,  "There  is  little 
doubt  that  the  distribution  of  life  in  the  sea  is  exactly  opposite  to  that 
on  the  land.  The  greatest  fisheries  are  those  of  the  temperate  and 
arctic  seas.  .  .  .  Nowhere  are  sea  birds  so  numerous  as  in  polar 
waters.  The  benthic  fauna  and  flora  are  also  most  luxuriant."  The 
Bay  of  Naples  has  a  "  richly  varied,  but  (in  mass)  a  scanty  fauna  and 
flora,"  and  "  at  the  very  least  the  amount  of  life  in  polar  seas  is  not 
less  than  in  the  tropics."2 

Marine  life  is  also  more  prolific  near  river  mouths  of  the  tem- 
perate zones,  probably  because  of  the  great  quantities  of  dissolved 
"  salts  of  nitrous  and  nitric  acid  and  ammonia,  and  other  substances 
which  are  the  ultimate  food-stuffs  of  the  plankton."  Just  outside  of 
the  estuary  of  the  Mersey  in  Lancashire  there  were  "not  less  than 
twenty,  and  not  more  than  two  hundred  animals  varying  in  size  from  an 
amphipod  (one  fourth  inch  long)  to  a  plaice  (eight  to  ten  inches  long) 
on  every  square  meter  of  bottom"  (Johnstone,  1909:  149,  176,  195-6). 
Finally  the  quantity  of  life  in  the  shallow  waters  of  the  sea  is  not 
directly  governed  by  favorable  habitat,  such  as  shallow  sunlight  waters 
in  constant  circulation  and  of  equable  temperature,  but  seems  to  be 
primarily  controlled  by  the  amount  of  the  minimal  food  elements. 
Sea-water  may  be  regarded  as  a  dilute  food-solution  having  the  essen- 
tial materials  on  which  life  is  dependent.  Of  these  nitrogen  and  the 
compounds  of  silica  and  phosphoric  acid  are  present  in  the  smallest 
amount.  Johnstone  tells  us  that  "  The  density  of  the  marine  plants 
will  therefore  fluctuate  according  to  the  proportions  of  these  indispen- 
sable food-stuffs"  (234).  "It  is  only  the  protophyta  among  the 

'"Life  in  the  Sea,"  1908,  201-205. 


1 8  THE  PALEONTOLOGIC  RECORD 

plankton  which  can  utilize  the  C02  and  the  nitric  acid  compounds, 
and  so  we  see  that  upon  these  rest  the  greater  part  of  the  task  of 
elaborating  the  dissolved  food-stuff  of  the  sea"  (239). 

Undoubtedly  much  of  the  land-derived  nitrogen,  estimated  at  38 
million  tons  per  annum,  is  used  up  in  the  shallow  areas  by  the  plants. 
We  therefore  arrive  at  the  conclusion  that  shallow  seas  bordering 
naked,  cold,  or  arid  lands  should  have  the  smallest  amount  of  life, 
and  that  those  of  temperate  regions  adjacent  to  low  lands  under  pluvial 
climates  should  have  the  greatest  number  of  individuals.  This  con- 
clusion, however,  may  be  decidedly  altered  by  the  oceanic  currents  in 
that  they  distribute  far  and  wide  the  salts  of  the  sea. 

These  factors  also  suggest  that  during  "  critical  periods "  the 
faunas  should  be  least  abundant  and  varied,  and  that  at  the  times  of 
extreme  base  levels  and  sea  transgressions  they  ought  to  be  at  their 
maximum  development.  These  suggestions  are  borne  out  by  the  small 
Cambric,  Permic  and  earliest  Eocene  faunas  and  the  large  cosmopolitan 
biotas  of  the  Siluric,  Jurassic  and  Oligocene  times. 

Sessile  algae  are  not  common  on  muddy  or  sandy  grounds,  and  these 
areas  in  the  present  seas  have  been  compared  with  the  desert  areas  of 
the  lands.  That  muddy  grounds  are  now  nearly  devoid  of  algous 
growth  has  particular  significance  in  stratigraphy,  because  in  the  geo- 
logic column  at  many  levels  and  in  nearly, all  regions  occur  black  shale 
formations  that  are  not  only  devoid  of  plant  fragments  but  are  also 
usually  very  poor  in  fossils  of  the  sessile  benthos.  When  the  latter  are 
present  it  is  seen  that  they  are  usually  thin-shelled  and  small  forms, 
or  are  types  of  organisms  that  live  in  the  upper  sunlight  realm  and 
are  either  of  the  swimming  plankton  or  the  floating  nekton.  As  ex- 
amples of  such  deposits  may  be  cited  the  widely  distributed  Utica  for- 
mation of  the  Ordovicic  extending  from  southern  Ohio  -to  Lake  Huron 
and  east  to  Montreal,  and  the  Genesee  (Devonic)  of  New  York.  In 
these  cases  what  appears  to  be  of  the  sessile  benthos  is  thought  to  be- 
long to  the  nekton  attached  to  floating  seaweeds  or  other  floating  ob- 
jects, and  eventually  all  of  the  life  of  the  nekton  and  the  plankton 
sinks  to  the  bottom  of  the  sea.  Therefore  the  carbonaceous  matter  of 
the  black  shales  may  be  of  algous  origin  like  that  of  the  New  York 
Genesee,  but  it  is  far  more  probable  that  it  is  largely  of  animal  origin, 
as  the  crude  petroleum  of  such  deposits  usually  has  the  optical  proper- 
ties of  animal  oil  and  especially  those  of  fish  oil.3  Plants  may  be  torn 
from  rocky  bottoms  of  the  shallow  areas  by  the  action  of  the  storms  and 
then  carried  by  the  currents  into  eddying  areas  like  the  present  Sar- 
gossa  Sea,  which  has  among  its  algae  a  very  characteristic  assemblage 
of  animals.  It  is  probable,  however,  that  black  shales  having  wide  dis- 
tribution were  more  often  the  deposits  in  closed  arms  of  the  sea  (cul 

'Dalton,  Economic  Geology,  1909,  627. 


THE  PALEONTOLOGIC  RECORD  19 

de  sacs),  or  when  of  small  areal  extent,  as  the  result  of  fillings  of  holes 
in  the  sea  bottom.  In  all  such  places  there  is  defective  circulation  and 
lack  of  oxygen  resulting  in  foul  asphixiating  bottoms. 

These  are  the  "  halistas  "  of  Walther  and  the  "  dead  grounds  "  of 
Johnstone.  To-day  such  are  the  Black  Sea  and  the  Bay  of  Kiel,  where 
sulphur  bacteria  abound  in  greatest  profusion.  These  decompose  the 
dead  organisms  that  rain  from  the  photic  region  into  such  suffocating 
areas,  or  the  carcasses  which  are  drawn  there  by  the  slow  undertow  from 
the  higher  ground.  These  bacteria  in  the  transforming  process  deposit 
in  their  cells  sulphur  that  ultimately  combines  with  the  iron  that  is  pres- 
ent and  replaces  the  calcareous  skeletons  of  invertebrates  by  iron  pyrite 
or  marcasite.  In  this  way  are  formed  the  wonderfully  interesting 
pseudomorphs  of  Triarthrus  becki,  the  Utica  trilobite  preserving  the 
entire  ventral  limbs,  and  of  the  other  well  preserved  but  small  inverte- 
brates from  the  Coal  Measures  black  shale  of  Danville,  Illinois. 

Brackish-water  and  especially  deep-sea  shelled  animals  tend  to  have 
thin  shells,  while  increase  of  salinity  tends  towards  the  thickening  and 
roughening  of  the  calcareous  shells.  It  is  a  well  known  fact  that  in  the 
dolomite-depositing  continental  seas  like  that  of  the  Guelph  (Siluric). 
all  of  the  molluscs  have  ponderous  thick  shells.  These  have  been  in- 
terpreted as  reef-living  species  but  actual  reefs  in  the  Guelph  are  un- 
known. The  molluscs  are  often  common  but  corals  are  represented  by 
but  a  few  species.  Similar  conditions  are  known  to  occur  in  other 
dolomite  faunas.  Further,  the  Guelph  was  of  a  time  of  decided  progres- 
sive emergence  and  restrictional  seas  under  an  arid  climate,  and  there- 
fore the  waters  must  have  been  abnormally  salty. 

Rivers  constantly  discharge  into  the  sea  great  quantities  of  plant 
material,  but  as  a  rule  little  of  it  other  than  the  wood  is  swept  far  out 
to  sea.  At  present  the  rivers  of  northern  Siberia  float  into  the  sea 
vast  numbers  of  logs  that  drift  with  the  currents  to  Spitzbergen,  East 
and  West  Greenland  and  Arctic  America.  This  wide  dispersal  of 
wood  by  the  sea  is  met  with  only  in  the  cold  regions,  whereas  in  trop- 
ical waters  the  wood  is  rapidly  decomposed.  Single  leaves  are  rarely 
transported  far  from  their  place  of  origin,  and  when  of  good  preserva- 
tion in  geologic  deposits,  give  decisive  evidence  of  the  nearness  of  the 
shore.  On  the  other  hand,  tough  palm  leaves  have  been  seen  in  the 
sea  70  miles  from  land  and  rafts  of  leaves  are  often  met  with  200  or 
more  miles  beyond  the  mouths  of  the  Kongo  and  the  Amazon.  Prox- 
imity to  shore  is  also  indicated  by  the  presence  in  marine  faunas  of 
land  molluscs,  insects  and  bones  of  land  vertebrates. 

With  tillites  now  known  in  the  Lower  Huronian  of  Canada,  in  the 
Lower  Cambric  of  northern  Norway,  China,  South  Africa  and  Aus- 
tralia, and  in  the  Permic  of  India,  South  Africa,  Australia  and  Brazil, 
we  observe  the  recurrence  of  glacial  climates.  The  Siluric  and  Devonic 


20  THE  PALEONTOLOGIC  RECORD 

coral  reefs  occurring  in  Arctic  regions,  the  sponge,  coral  and  bryozoa 
reefs  in  the  Jurassic  of  northern  Europe,  the  rudistid  and  other 
cemented  pelecypods  in  reefs  of  wide  distribution  in  the  Cretaceous, 
and  the  almost  world- wide  distribution  of  the  Nummulitidae  (north  of 
Siberia)  in  the  late  Eocene  and  Oligocene  point  as  clearly  to  warm 
waters  and  mild  polar  climates.  Further  the  widely  distributed  Car- 
bonic foraminifers  of  the  family  Fusulinidae  that  swarmed  in  temper- 
ate and  tropical  regions  are  unknown  to  Arctic  and  Antarctic  regions. 
In  other  words,  long  before  we  have  a  fossil  record  the  earth  had  cli- 
matic zones,  and  for  long  periods  the  climate  was  mild  to  warm, 
punctuated  by  shorter  intervals  of  cold  to  mild  climates. 

The  volume  of  sea  water  to-day  is  very  great,  but  we  must  ask  our- 
selves: Has  this  quantity  always  been  such  or  was  it  even  greater,  as 
some  geologists  still  hold?  We  no  longer  agree  with  Laplace  and 
Dana  that  the  earth  passed  through  an  astral  stage,  but  rather  agree 
with  Chamberlin  that  it  always  has  had  a  more  or  less  cold  exterior. 
Through  volcanic  activity  much  juvenile  water  from  the  interior  of  the 
earth  was  extruded  in  geologic  time  and  was  added  to  the  vadose  waters 
of  the  surface.  Suess  states  that  "  the  body  of  the  earth  has  given  forth 
its  oceans  and  is  in  the  middle  phase  of  its  gas  liberations."  Accord- 
ingly, the  Paleozoic  oceans  must  have  been  quantitatively  smaller  than 
those  of  the  present,  and  the  gradual  increase  in  the  volume  of  vadose 
waters  has  been  accommodated  by  the  periodic  increase  of  oceanic 
depth. 

We  also  agree  with  Walther  that  the  oceans  of  Paleozoic  and  earlier 
time  did  not  have  the  great  abyssal  depths  they  now  have.  The  ac- 
centuated deepening  of  the  permanent  oceanic  basins  did  not  begin 
until  the  Triassic,  for  in  none  of  the  great  depths  of  the  present  oceans 
are  found  traces  of  Paleozoic  organisms,  and  all  here  are  of  Mesozoic 
or  Tertiary  origin.  In  the  shallow  regions,  however,  are  still  found 
a  few  Paleozoic  testaceous-bearing  genera  of  brachiopods,  tubicular 
annelids,  pelecypods,  gastropods,  Nautilus,  and  Limulus.  The  deepen- 
ing of  the  Pacific,  the  Indian,  and  especially  the  Atlantic  oceans  has 
been  at  the  expense  of  the  lands  or  horsts,  for  the  ancient  continents, 
Gondwana  and  Laurentia,  have  each  towards  the  close  of  the  Mesozoic 
been  broken  into  several  masses.  We  may  therefore  speak  of  permanent 
oceans,  and  transgressed,  fractured,  and  partially  down  faulted,  con- 
tinents or  horsts. 

These  are  some  of  the  factors  that  control  the  making  of  some  of 
the  modern  paleogeographic  maps. 


THE  PALEONTOLOGIC  RECORD  21 

BIOLO.GIC  PRINCIPLES  OP  P ALE 0 GEOGRAPHY 

BY  DE.  F.  H.  KNOWLTON 

U.   S.  GEOLOGICAL  SUBVEY 

/CONSIDERING  the  breadth  and  intricacy  of  the  subject  assigned 
^^  me,  and  the  limited  time  that  can  be  given  to  its  consideration, 
it  has  seemed  best  to  me  to  restrict  my  remarks  to  two  or  three  of  the 
obviously  more  important  phases  of  the  problem. 

Aside  from  the  study  of  the  rock-masses  themselves — which  are 
often  difficult  of  interpretation — relianceifor  an  interpretation  of  paleo- 
geography  must  be  placed  in  the  former  life  found  entombed,  and  of 
the  two  biologic  elements,  plants  undoubtedly  hold  a  very  high — prob- 
ably the  highest — place. 

In  making  use  of  plants  in  the  study  of  paleogeography  we  may 
first  consider  distribution.  If  we  find  two  fossil  floras  identical  or 
similar  in  all  essential  or  important  details,  we  feel  justified  in  re- 
garding them  for  all  practical  geologic  purposes  as  contemporaneous. 
In  order  that  we  may  be  certain  that  the  two  floras  are  identical,  they 
must  be  composed  of  types  that  are  readily  identifiable,  that  is,  forms 
so  well  characterized  that  they  may  be  easily  and  certainly  recognized. 
As  examples  of  such  floral  elements  mention  may  be  made  of  many 
ferns  and  fern  allies,  most  cycads,  conifers  and  peculiar,  well-marked 
or  characteristic  dicotyledons.  Having  settled  the  contemporaneity  of 
the  floras,  inquiry  may  next  be  made  as  to  the  probable  manner  in 
which  the  separated  or  isolated  areas  were  reached  by  these  floras. 
Here  again  we  must  carefully  consider  the  character  of  the  flora  and 
the  means  for  its  natural  dispersal.  The  living  flora,  and  for  that 
matter  probably  the  floras  from  at  least  the  beginning  of  the  Tertiary 
progressively  to  the  present  time,  has  developed  in  many  ways  means 
for  the  comparatively  rapid  and  wide-spread  dissemination  of  their 
reproductive  parts  (seeds,  etc.).  For  example,  a  large  percentage  of 
the  members  of  the  dominant  living  family  of  seed-plants — the  Com- 
posite— have  developed  seeds  with  an  attachment  of  soft,  fluffy  hairs 
which  serve  to  float  them  in  the  air,  often  to  great  distances.  In  many 
other  living  groups  there  are  similar,  or  at  least  as  effective,  devices 
for  dissemination,  but  as  we  go  back  in  time  adaptations  calculated  to 
be  of  aid  in  distribution  grow  less  and  less,  and  soon  even  seeds  of  any 
kind  are  unknown,  or  known  but  imperfectly,  and  reproduction  is 
normally  by  means  of  spores,  that  is,  reproductive  bodies  in  which  there 
is  no  embryo  already  formed  when  they  leave  the  parent  plant.  It  is 
obvious  that  plants  that  are  reproduced  by  seeds,  in  which  there  is 
both  an  embryo  and  a  supply  of  food  for  use  during  germination,  must 
possess  a  decided  advantage  over  those  reproduced  by  means  of  spores. 


22  THE  PALEONTOLOGIC  RECORD 

In  the  groups  of  spore-bearing  plants  ordinarily  found  fossil,  the 
spores  are  not  known  to  have  developed  any  particular  devices  for  their 
wide  dissemination,  such  as  flotation  in  air,  attachment  to  animals,  etc. 
They  are  produced  in  vast  quantities,  and  depend  upon  a  few  reach- 
ing situations  favorable  for  successful  germination.  Their  vitality  is 
also  of  apparently  exceedingly  limited  duration,  and  it  is  doubtful  if 
they  could  long  survive  immersion  in  salt  water. 

The  bearing  of  the  above  digression  is  apparent.  Given  a  fossil 
flora  made  up  of  ferns  or  fern  allies,  exclusive  of  what  are  known  to 
belong  to  the  cycadofilices,  and  when  such  flora  is  found  in  two  or  more 
separated  areas,  we  are  justified,  in  my  opinion,  in  arguing  a  practically 
continuous  land  connection.  They  were  incapable  of  crossing  very  wide 
reaches  of  open  water,  particularly  salt  water.  Fresh-water  streams 
have  been  to  some  extent  avenues  of  distribution,  but  many  fossil 
floras — and  living  floras  as  well — are  too  widely  spread  to  be  explained 
by  this  means.  "When,  as  is  usually  the  case,  identical  floras  occupying 
different  areas  are  mixed  floras,  the  bearing  on  the  means  of  reaching 
the  various  areas  is  more  complicated.  An  example  may  better  serve 
to  bring  this  out.  Thus,  the  Jurassic  flora  is  practically  world-wide 
in  its  distribution,  ranging  from  Franz  Josef  Land,  82°  N".,  to  Louis 
Philippe  Land,  63°  S.  It  is  composed  of  ferns,  fern-allies,  cycads  and 
conifers,  a  large  percentage  being  true  ferns.  The  probability  of  a 
close  land  connection  argued  on  the  basis  of  the  true  ferns,  has  already 
been  alluded  to.  The  cycads — the  Jurassic  is  called  the  age  of  cycads 
— were  abundant  in  individuals  and  numerous  in  forms.  On  the  basis 
of  our  knowledge  of  living  types,  it  may  be  stated  that  cycad  seeds 
germinate  immediately  on  falling  from  the  cone  without  any  necessary 
resting  period.  They  are  not  known  to  retain  their  vitality  for  a 
longer  period  than  three  years,  and  usually  but  two  years.  They  sink 
promptly  in  fresh  water  and  as  the  stony  coat  is  easily  penetrated  by 
water,  they  either  germinate  or  rot  at  once.  In  salt  water  they  will 
probably  sink  and  decay  even  more  quickly.  Therefore,  the  probability 
of  their  being  transported  for  any  great  distance  over  open  water  is 
reduced  to  a  minimum.  The  conifers  of  the  Jurassic  were  reproduced 
by  seeds.  They  belong  to  types  not  known  to  enjoy  any  special  means 
for  transportation,  nor  is  it  probable  they  could  better  withstand  fresh- 
or  salt-water  immersion  than  the  cycads.  All  classes  of  vegetation 
present  in  the  Jurassic,  therefore,  argue  for  a  practically  continuous 
land  connection. 

In  considering  the  bearing  of  any  flora  on  the  paleogeographic 
problem  the  process  is  similar  to  that  outlined  above.  That  is,  an 
analysis  of  the  composition  of  the  flora,  a  study  of  the  means  of  nat- 
ural dissemination  which  includes  duration  of  vitality,  and  finally  a 
judgment  as  to  its  probable  means  or  avenues  of  transportation,  in- 
volving a  land  connection  or  otherwise. 


THE  PALEONTOLOGIC  RECORD  23 

A  word  may  be  said  as  to  the  presence  of  land  plants  in  marine  de- 
posits. That  the  trunks  of  trees  may  float  for  a  considerable  time  and 
to  great  distances  is  undeniably  possible,  but  unfortunately  the  study 
of  fossil  wood  has  not  yet  reached  that  degree  of  refinement  in  most 
cases  that  will  permit  of  its  general  use,  and  reliance  in  identification 
must  be  placed  largely  in  foliar  and  reproductive  organs.  The  delicate 
fronds  of  ferns,  leaf-clad  branchlets  of  conifers  and  the  leaves  of  seed- 
bearing  plants  are  incapable  of  long  withstanding  the  immersion  and 
wave  action  of  salt  waters.  In  my  judgment,  therefore,  the  presence 
of  fronds,  leaves  and  similar  organs  in  marine  deposits  argues  very 
near-by  land. 

The  only  other  point  I  shall  consider  is  the  bearing  of  plants  on  the 
interpretation  of  climate.  Since  it  is  generally  acknowledged  that 
plants  furnish  the  most  reliable  data  for  this  phase  of  the  subject,  an 
inquiry  as  to  the  kinds  of  plants  that  have  been  found  most  valuable 
in  this  connection  may  be  of  interest.  Obviously  our  interpretation  of 
the  probable  conditions  under  which  the  plants  of  past  geological  ages 
grew,  must  be  on  a  basis  of  a  knowledge  of  present  conditions  found 
to  obtain  for  similar  or  closely  related  groups.  That  we  may  occasion- 
ally err  in  this  is  possible,  especially  if  reliance  is  based  on  too  few 
forms,  but  when  all  the  various  elements  of  a  flora  are  considered,  the 
results  are  thought  to  be  within  a  close  approximation  of  the  truth. 
Thus,  since  Artocarpus — the  bread-fruit  tree — only  grows  at  the  pres- 
ent day  within  20°  of  the  equator,  it  follows  that  when  Artocarpus  is 
found  fossil  in  Greenland,  72°  N.,  the  conditions  at  the  time  it 
flourished  there  must  have  been  tropical  or  subtropical,  and  this  con- 
clusion is  confirmed  by  the  tree  ferns  and  cycads  associated  with  it. 
Palms  can  not  flourish  with  a  temperature  below  40°;  a  fossil  flora, 
rich  in  palms  of  well-defined  types,  could  hardly  have  grown  under 
very  much  cooler  conditions.  Tree-ferns  are  practically  confined  to 
within  30°  of  the  equator  and  a  temperature  of  approximately  60°.  A 
fossil  flora,  such,  for  example,  as  the  Triassic  of  Virginia,  that  contains 
numbers  of  tree-ferns,  must  have  grown  under  tropical  or  subtropical 
conditions.  A  fossil  flora  rich  in  types,  the  living  representatives  of 
which  can  withstand  a  temperature  of  — 40°  to  —  60°,  or  even  lower, 
must  have  been  at  least  cool-temperate.  Cycads  are  now  found  only 
within  30°  of  the  tropics;  a  rich  cycad  flora  argues  then  for  a  tropical 
or  at  least  a  subtropical  climate. 

Examples  of  this  kind  could  be  multiplied  almost  indefinitely.  In 
interpreting  geological  climate  selection  is  made  so  far  as  possible  of 
the  plants  or  groups  of  plants,  that  are  confined  at  the  present  day 
within  relatively  narrow  limits  of  temperature,  be  this  high,  medium 
or  low. 


24         THE  PALEONTOLOGIC  RECORD 


PALEONTOLOGIC  EVIDENCES  OF  CLIMATE 


BY  T.   W.   STANTON 

U.    S.    GEOLOGICAL    SURVEY 


nnO  every  one  climate  is  an  interesting  theme.  The  climates  of  the 
-L  past,  especially  when  they  can  be  shown  to  differ  in  character 
or  distribution  from  those  of  the  present,  attract  the  attention  of  the 
general  public,  and  they  are  of  importance  to  the  special  student  of 
geologic  history  whether  his  researches  deal  with  the  purely  physical 
aspects  of  the  subject  or  include  some  branch  of  paleontologic  study. 

The  evidence  as  to  former  climates  comes  from  many  sources.  The 
records  of  deposition  and  denudation  in  themselves  sometimes  give 
more  or  less  definite  indications  concerning  variations  in  temperature 
or  moisture  or  both;  the  land  floras  when  compared  with  those  now 
living  by  their  general  characters  and  by  the  details  of  their  structure, 
show  more  or  less  clearly  the  climatic  conditions  under  which  they 
lived ;  the  land  animals,  especially  the  higher  vertebrates,  afford  a  good 
basis  for  inferring  their  habits  and  hence  indirectly  their  environment, 
including  climate;  marine  invertebrates  give  trustworthy  evidence  of 
differences  in  temperature  of  oceanic  littoral  waters  at  least  in  the  later 
periods.  It  is  obvious,  however  that  the  data  furnished  by  any  one  of 
these  lines  of  evidence  will  make  only  unconnected  fragments  of  the 
history  of  past  climates  and  that  the  evidence  on  the  climate  of  any 
particular  epoch,  if  derived  from  a  single  source,  is  seldom  so  complete 
or  so  convincing  that  corroborative  testimony  from  other  sources  is  not 
desirable.  The  subject  is  one  in  which  general  cooperation  is  essential. 

It  should  be  stated  at  the  outset  that  the  most  abundant  and  most 
definite  evidence  comes  from  paleobotany,  and  will  be  outlined  in  Mr. 
White's  paper.  The  discussion  of  the  data  derived  from  fossil  verte- 
brates must  also  be  left  for  some  one  who  is  qualified  to  present  it,  and 
the  whole  Paleozoic  era  may  be  passed  over  with  the  statement  that  so 
far  as  indications  from  the  animal  life  are  concerned  the  climate  of 
the  whole  earth  was  mild  and  equable.  The  proof  of  local  exceptions 
to  this  statement  comes  from  other  sources. 

All  inferences  from  paleontologic  evidence  as  to  former  climatic 
conditions  rest  in  the  final  analysis  on  a  comparison  with  the  present 
distribution  of  animals  and  plants  with  reference  to  climate.  Such 
comparisons  may  be  general  or  specific,  direct  or  indirect,  and  the  con- 


THE  PALEONTOLOGIC  RECORD  25 

elusions  that  may  be  drawn  from  them  vary  greatly  in  positiveness. 
To  take  a  familiar  example,  the  reef-building  corals  are  now  restricted 
to  shallow  waters  in  which  the  mean  temperature  during  the  coldest 
month  in  the  year  is  not  less  than  68°  F.,  and  such  conditions  are  not 
found  in  the  northern  hemisphere  north  of  latitude  32°.  Since  late 
Tertiajy  corals  differ  but  little  from  those  of  the  present  time  it  is 
justifiable  to  assume  that  coral  reefs  in  late  Tertiary  rocks  indicate 
waters  of  about  the  temperature  stated.  But  when  Jurassic  coral  reefs 
are  found  as  far  north  as  latitude  53°  it  is  by  no  means  so  certain  that 
they  indicate  a  minimum  monthly  mean  temperature  of  68°  F.,  and 
concerning  Devonian  and  Silurian  coral  reefs  in  high  latitudes  the 
doubt  must  be  still  greater.  At  the  present  time  large  reptiles  are 
mainly  confined  to  hot  moist  climates,  but  that  fact  alone  can  not  be 
considered  proof  that  the  Mesozoic  dinosaurs  required  the  same  kind 
of  a  climate. 

The  impress  of  climate  on  the  present  fauna  is  shown  in  various 
ways.  A  tropical  fauna  contains  the  greatest  number  of  species  and 
exhibits  its  luxuriance  in  other  ways.  Thus,  taking  shell-bearing 
marine  mollusks  to  illustrate  the  general  law,  Dall  has  shown  in  Bul- 
letin 84,  U.  S.  Geological  Survey,  that  the  average  tropical  fauna  in 
shallow  waters  consists  of  over  600  species,  while  the  temperate  fauna 
has  less  than  500  species,  and  the  boreal  fauna  only  250.  Again,  there 
are  certain  genera  that  are  characteristic  of  particular  zones,  and  as- 
semblages of  forms  that  are  recognized  as  belonging  only  to  frigid,  or 
temperate,  or  tropical  waters,  and  in  genera  that  have  a  wide  range 
many  of  the  species  are  restricted  to  certain  limits  of  temperature. 

In  the  late  Tertiary  faunas  which  contain  a  large  proportion  of 
living  genera  and  many  living  species  justifiable  inferences  as  to  climate 
may  be  made  from  direct  comparison  with  living  faunas.  By  one  or 
another  of  the  tests  just  indicated,  or  by  a  combination  of  them,  Dall 
has  produced  convincing  evidence  that  the  Oligocene  fauna  of  the 
Atlantic  states  was  subtropical  and  that  the  Oligocene  maintains  its 
subtropical  character  even  as  far  north  as  Arctic  Siberia.  He  has  also 
shown  that  the  Miocene  fauna  of  Maryland  indicates  a  temperate 
climate  and  that  a  similar  cool-water  fauna  extended  at  that  time  as 
far  south  as  Florida.1  The  fossils  of  the  raised  Pliocene  beaches  at 
Nome,  Alaska,  according  to  the  same  investigator,  furnish  evidence  of 
warmer  climate  during  Pliocene  time  even  at  that  high  latitude.  By 
similar  methods,  in  a  paper  published  in  the  Journal  of  Geology,  Vol. 
XVII.,  Arnold  has  recently  argued  for  a  series  of  climatic  changes  in 
the  late  Tertiary  and  Pleistocene  of  California. 

When  the  investigation  is  carried  back  to  the  Mesozoic  and  earlier 

1  See  especially  Dall's  "  Contributions  to  the  Tertiary  Fauna  of  Florida," 
published  as  Vol.  III.  of  the  Transactions  of  the  Wagner  Free  Institute  of 
Science,  Philadelphia,  and  a  chapter  in  the  Miocene  volume  of  the  Maryland 
Geological  Survey. 


26  THE  PALEONTOLOGIC  RECORD 

faunas  in  which  few  of  the  genera  and  none  of  the  species  are  identical 
with  those  now  living  the  problem  becomes  more  difficult  and  the  con- 
clusions are  much  less  definite,  as  the  comparisons  must  be  more  gen- 
eral. Proofs  of  actual  temperatures  as  measured  in  degrees  should  not 
be  expected  unless  the  botanists  can  furnish  data.  There  is,  however, 
great  local  differentiation  of  faunas  and  it  is  fair  to  ask  the  question 
to  what  extent  this  is  due  to  differences  in  climate.  One  of  the  earliest 
discussions  of  this  question  was  by  Ferdinand  Roemer,  who  more  than 
fifty  years  ago  in  "  Die  Kreidebildungen  von  Texas  "  noted  the  fact 
that  the  Cretaceous  of  the  highlands  in  Texas  is  lithologically  and 
faunally  much  like  the  Cretaceous  of  southern  Europe  and  the  Medi- 
terranean region,  that  it  differs  from  the  Cretaceous  of  New  Jersey  in 
about  the  same  way  that  the  southern  European  Cretaceous  differs  from 
that  of  England  and  northwestern  Germany,  and  that  in  each  case  the 
European  deposit  is  approximately  10°  farther  north  than  its  American 
analogue.  He  concluded  that  the  differences  between  the  northern  and 
southern  facies  were  due  to  climate  and  that  the  climatic  relations  be- 
tween the  two  sides  of  the  Atlantic  were  about  the  same  in  Cretaceous 
time  as  they  are  now.  Roemer's  conclusion  that  there  were  climatic 
zones  in  the  Cretaceous  may  be  true,  but  his  reasoning  was  based  on 
false  premises  so  far  as  the  American  deposits  are  concerned,  for  the 
New  Jersey  type  of  marine  Cretaceous  extends  with  little  change  all 
the  way  from  New  Jersey  to  the  Rio  Grande,  and  the  "  Cretaceous  of 
the  highlands "  with  which  he  contrasted  it,  now  known  as  the 
Comanche  series,  is  not  represented  by  marine  beds  on  the  Atlantic 
coast.  This  shows  the  necessity  for  careful  stratigraphic  and  areal 
work  as  well  as  for  good  paleontology  before  such  broad  conclusions 
can  be  safely  made. 

The  more  general  work  of  Neumayr2  recognized  in  the  Jurassic 
and  Cretaceous  of  Europe  three  fauna!  provinces  designated  as  boreal, 
central  European,  and  alpine  or  equatorial,  which  on  account  of  their 
zonal  distribution  he  regarded  as  indicating  climatic  differences.  He 
believed  that  these  zones  are  recognizable  throughout  the  northern 
hemisphere  and  cited  evidence  to  show  that  similar  zones  exist  south  of 
the  equator.  In  recent  years  Neumayr's  conclusions  have  been  ques- 
tioned by  many  because  in  so  many  instances  genera  supposed  to  be 
characteristic  of  one  zone  have  been  found  mingled  with  those  of 
another.  For  example,  the  alpine  ammonite  genera  Lytoceras  and 
Phylloceras  occur  in  Alaska  (lat.  60°)  associated  with  the  boreal 
Aucella,  and  Aucella  itself  ranges  from  the  Arctic  Ocean  to  the  torrid 
zone.  Still,  in  spite  of  such  exceptions  and  anomalies  in  distribution, 
there  is  much  evidence  for  a  real  distinction  between  boreal  and  south- 
ern faunas  in  the  Jurassic  and  in  the  Cretaceous  which  may  indicate 
a  zonal  distribution  of  temperature  in  Mesozoic  time.  It  should  be 

2 "  Erdgeschichte,"  Vol.  II.,  p.  330  et  seq. 


THE  PALEONTOLOGIC  RECORD  27 

remembered,  however,  that  a  boreal  climate  probably  did  not  then  mean 
a  frigid  climate,,  and  that  the  differences  in  temperature  were  probably 
not  so  great  as  at  the  present  time. 

The  conclusions  justified  by  the  evidence  from  fossil  invertebrates 
are: 

1.  In  the  Paleozoic  there  is  practically  no  faunal  evidence  of  cli- 
matic zones  comparable  with  those  that  now  exist. 

2.  In  the  Mesozoic  there  is  a  more  or  less  definite  zonal  distribution 
of  faunas  which  may  be  in  part  due  to  differences  in  climate  but  this 
conclusion  in  each  case  should  be  checked  by  the  study  of  the  floras  and 
all  other  available  lines  of  evidence. 

3.  From  the  middle  of  the  Tertiary  on  through  the  Pleistocene  trust- 
worthy conclusions  as  to  climatic  conditions  and  changes  can  be  made 
by  direct  comparisons  with  the  distribution  of  living  faunas. 

THE  MIGRATION  AND  SHIFTING  OF  DEVONIAN  FAUNAS 

BY  PKOFESSOR  HENRY   S.  WILLIAMS 

CORNELL    UNIVERSITY 

IN  the  year  1881  I  presented  before  the  American  Association  for 
the  Advancement  of  Science  the  first  definite  announcement  of 
the  theory  of  recurrent  faunas,  applying  it  to  the  fauna  of  the  Mar- 
cellus,  Genesee  and  Ithaca  black  shales  of  New  York,  which  I  then 
conceived  to  be  represented  by  the  continuous  fauna  of  the  black  shales 
of  Ohio,  Indiana,  Kentucky  and  Tennessee ;  and  also  in  the  same  paper 
the  theory  of  shifting  of  faunas  was  applied  to  the  Hamilton  and  Che- 
mung  faunas  of  central  New  York.1  Since  that  time  a  large  amount  of 
evidence  has  been  accumulated  confirming  these  hypotheses. 

The  two  hypotheses  are  correlated.  Recurrence,  or  the  departure  of 
a  fauna,  its  replacement  by  another  and  its  final  reappearance  in  the 
same  section  at  a  higher  level,  become  the  facts  upon  which  the  hypoth- 
esis of  shifting  of  the  faunas  is  based;  and  only  on  the  assumption  of 
the  continuance  and  shifting  of  a  fauna  without  losing  its  character- 
istics can  we  satisfactorily  explain  its  recurrence. 

The  following  facts  are  among  the  more  important  which  have  come 
to  light  in  the  course  of  my  studies : 

§  1.  The  Catskill  sedimentation  was  shown  to  be  thicker  and  to  start 
lower  down  in  the  geological  column  in  eastern  New  York  than  in 
middle  and  western  New  York.  In  eastern  New  York  it  began  while 
the  Hamilton  marine  fauna  was  still  present  and  cut  it  off,  bringing  in 
estuarian  conditions  with  a  brackish  water  and  land  fauna  and  flora. 
In  middle  New  York  no  Catskill  sedimentation  is  present  until  after 

1  Proo.  American  Association  for  the  Advancement  of  Science,  Vol.  XXX., 
p.  186,  etc. 


28  THE  PALEONTOLOGIC  RECORD 

the  arrival  of  the  Chemung  fauna ;  and  in  western  New  York  no  trace 
of  the  Catskill  type  of  sediments  appears  till  after  the  close  of  the 
Devonian. 

These  facts  are  direct  evidence  of  shifting  of  the  environmental 
conditions  of  the  edge  of  the  continent  westward  as  the  deposits  of  the 
middle  and  upper  Devonian  were  being  laid  down.  With  this  shifting 
westward  of  the  off-shore  conditions  of  the  sea,  there  went  on  a  corre- 
sponding shifting  of  several  faunas  that  were  adjusted  to  each  phase  of 
those  conditions. 

These  facts  were  stated  in  a  paper  on  the  classification  of  the  upper 
Devonian  published  in  1885. 2 

§  2.  The  Appearance  of  Dominant  Species  of  a  General  Fauna  in 
Reversed  Order  of  Succession  at  the  Close  of  a  Fossiliferous  Zone. — 
The  case  of  Spirifer  Icevis  in  the  Ithaca  Zone  and  of  the  frequent  ap- 
pearance of  Leiorhynchus  at  the  opening  and  close  of  a  fossiliferous 
zone  were  among  the  earliest  observed  facts  suggesting  the  actual  shift- 
ing of  the  body  of  the  fauna  entering  the  area  in  one  order  of  succession 
and  its  departure  in  the  reverse  order.  In  the  Ithaca  section  there 
occurs  at  the  base  of  the  fossiliferous  zone  of  the  Ithaca  member  a  bed 
containing  abundance  of  Spirifer  (Reticularia)  Icevis.  The  discovery 
of  the  same  species  at  the  top  of  the  fossiliferous  zone  as  the  normal 
Ithaca  fauna  become  sparse  gave  the  first  suggestion  that  the  faunas 
were  moving  or  shifting.  The  Eeticularia  zone  marked  the  first  trace 
of  the  fauna  to  enter  and  the  last  to  leave  the  area.  Confirmatory  evi- 
dence was  also  found  in  the  order  of  succession  of  the  dominant  species 
of  the  Ithaca  fauna.  These  facts  were  reported  in  1883.3 

§  3.  The  study  of  the  mode  of  occurrence  of  Leiorhynchus  still  fur- 
ther drew  attention  to  the  definite  order  in  which  series  of  species  came 
in  and  went  out  of  any  given  area.  The  species  of  the  genus  were 
generally  found  abundantly  at  the  base  or  at  the  top  of  the  fossiliferous 
zones  rich  in  the  brachiopods  in  the  midst  of  which  Leiorhynchus  was 
rare.4 

§  4.  The  reappearance  in  a  single  or  few  strata  of  several  represen- 
tatives of  an  earlier  fauna  long  after  the  formation  to  which  they  were 
normal  had  ceased. 

Slight  traces  of  this  fact  were  observed  in  the  first  survey  of  the 
Devonian  section  passing  through  Ithaca,  reported  in  1883,  Bull.  3, 
U.  S.  G.  S.,  and  the  fauna  No.  14  N  (p.  15)  was  called  a  recurrent 
Hamilton  fauna  because  of  the  appearance  there  of  such  species  as 
Spirifer  fimbriatus,  S.  augustus,  Pleurotomaria  capillaria  and  others; 

2Proc.  American  Association  for  tJie  Advancement  of  Science,  XXXIV., 
p.  222. 

8  Bull.  3,  U.  S.  G.  S.,  p.  20,  and  1885  Proc.  A.  A.  A.  8.,  Vol.  XXXIV.,  p. 
222,  etc. 

4  See  Bull.  3,  U.  S.  G.  S.,  pp.  16  and  17,  1883. 


THE  PALEONTOLOGIC  RECORD  29 

and  higher  up  in  the  midst  of  the  Chemung  section  at  Chemung  nar- 
rows Tropidoleptus  carinatus  and  Cypricardella  bellistriata,  Phacops 
bufo  and  Dalmanites  calliteles  were  found. 

The  discovery  of  such  traces  of  an  earlier  fauna  led  to  further 
search;  and  as  the  evidence  accumulated  an  elaboration  and  definite 
formufotion  of  the  theory  of  recurrence  of  faunas  was  made  which  has 
been  set  forth  in  several  papers,  and  is  illustrated  in  detail  in  the  folio 
of  the  Watkins  Glen-Catatonk  quadrangles,  which  is  now  in  press,  for 
the  U.  S.  Geological  Survey  (December,  1909). 

The  facts  there  brought  out  are  substantially  as  follows :  There  are 
exhibited  in  the  sections  mapped  for  the  quadrangles  two  series  of  fos- 
siliferous  zones;  the  separate  zones  of  the  two  series  alternate  in  suc- 
cession; the  zones  of  one  series  dominate  the  western  sections  of  the 
area  and  thus  thin  out  or  disappear  on  tracing  them  eastward ;  the  zones 
of  the  second  series  dominate  the  eastern  sections  and  particularly  the 
whole  eastern  New  York  sections,  but  thin  out  westward  and  in  some 
cases  are  entirely  wanting  in  sections  west  of  the  Watkins  Glen  quad- 
rangle. The  first  set  of  faunal  zones  includes  the  faunas  of  the  Gene- 
see  shale,  the  Portage  formation  and  the  several  divisions  of  the 
Chemung  formation. 

The  second  set  of  zones  includes  the  Hamilton  fauna  proper  and 
recurrent  representatives  of  that  fauna  which  I  have  named  the  Para- 
cyclas  lirata  zone,  the  Spirifer  mesistrialis  zone,  the  LeiorJiynchus 
globuliformis  or  Kattel  Hill  zone.  These  zones  are  represented  by  the 
typical  Ithaca  group  of  Hall  in  its  typical  sections  at  Ithaca ;  and  above 
them  appear  the  first,  second  and  third  recurrent  Tropidoleptus  faunas 
(which  I  originally  named  the  Van  Etten,  the  Owego  and  the  Swart- 
wood  Tropidoleptus  zones,  respectively).  All  of  these  several  fossilifer- 
ous  zones  of  the  second  set  become  decidedly  thin  on  passing  westward 
across  the  region.  The  Ithaca  fauna  is,  occasionally,  detected  west  of 
the  Watkins  Glen  quadrangle,  but  is  confined  to  less  than  100  feet  thick- 
ness at  Watkins,  is  recognized  for  three  hundred  feet  at  Ithaca  and 
ranges  through  at  least  600  feet  along  Tioughnioga  Eiver. 

Only  a  slight  trace  of  the  Paracyclas  zone  is  seen  as  far  west  as 
Ithaca,  but  it  is  well  expressed  in  the  section  on  the  east  side  of  the 
area.  The  Van  Etten,  Owego  and  Swartwood  Tropidoleptus  zones 
appear  in  thin  tongues  of  strata  as  far  west  as  the  Waverly  quadrangle 
and  are  seen  in  occasional  traces  as  far  west  as  the  Elmira  quadrangle. 
When  followed  eastward  they  appear  to  blend  together  as  a  modified 
Hamilton  fauna  sparsely  appearing  in  the  strata  up  to  the  income  of 
the  Catskill  type  of  sedimentation. 

Where  the  Hamilton  recurrent  zones  are  seen  in  sharpest  expression 
the  recurrent  species  range  through  only  a  foot  or  a  few  feet  of  strata, 
hold  in  abundance  four  or  five  characteristic  Hamilton  species  such  as 


30  THE  PALEONTOLOGIC  RECORD 

Tropidoleptus  carinatus,  Cypricardella  ~bellistriata,  Rhipidomella  van- 
uxemi,  Spirifer  marcyi  and  Delthyris  mesacostalis  (=D.  consobrinus) 
and  others;  and  the  Owego  and  Swartwood  zones  appear  in  the  midst 
of  a  characteristic  Chemung  fauna  both  above  and  below  them.  In  the 
Owego  recurrent  zone  both  Phacops  rana  and  Dalmanites  calliteles 
occur. 

The  Van  Etten  recurrent  zone  lies  entirely  below  the  range  of 
Spirifer  disjunctus  and  associated  species  of  the  Chemung  formation. 
On  following  the  sections  eastward  from  the  Waverly  quadrangle  the 
species  of  the  Chemung  fauna  become  scarce,  and  east  of  the  Chenango 
Eiver  very  few  species  of  the  typical  Chemung  fauna  have  been  detected 
— although  they  are  still  abundant  in  the  Chemung  rocks  to  the  south- 
east and  southward  across  Pennsylvania,  Maryland  and  Virginia. 

§  5.  These  facts  have  been  interpreted  as  evidence  not  only  of  a 
general  shifting  of  faunas  coincident  with  a  rising  of  the  land  along 
the  eastern  edge  of  the  present  continent,  but  of  oscillation  of  condi- 
tions and  alternate  occupation  of  the  area  by  two  sets  of  faunas  coming 
from  opposite  directions  and  temporarily  living  in  abundance  in  the 
area  of  central  New  York. 

§  6.  The  lithologic  changes  in  the  sediments  containing  the  different 
faunas  are  not  sufficient  to  account  for  the  change  in  fauna.  In  quite 
a  number  of  sections  there  is  no  appreciable  difference  in  lithologic 
constitution  between  the  strata  which  for  a  hundred  feet  thickness 
have  been  filled  with  characteristic  Chemung  species  and  the  imme- 
diately following  thin  zone  (of  a  foot  or  two)  with  scarcely  a  trace  of 
the  Chemung  species,  but  holding,  in  great  number,  species  which  if 
found  by  themselves  would  be  undisputed  evidence  of  the  Hamilton 
formation. 

§  7.  It  becomes  necessary  therefore  to  suppose  that  the  controlling 
cause  determining  the  presence  of  one  or  other  fauna  is  not  the  char- 
acter of  the  bottom  on  which  the  sediments  which  preserved  the  fauna 
were  laid.  We  are  thus  led  to  conclude  that  the  qualities  of  the  ocean 
water  have  determined  the  shifting  or  migration  of  the  faunas.  The 
conditions  to  which  the  faunas  were  adjusted  were  evidently  those  of 
depth,  salinity  or  temperature  of  the  waters  in  which  the  species  lived ; 
and  their  change  of  habitation  was  occasioned  by  change  in  the  direc- 
tion, path  or  extent  of  flow  of  oceanic  currents. 

This  leads  us  to  consider  the  principles  of  migration  as  affecting 
marine  organisms. 

§  8.  Migration  of  Species  and  Shifting  of  Faunas. — Migration  as 
commonly  applied  in  natural  history  means  the  movement  of  large 
numbers  of  the  same  species  from  one  place  to  another  in  a  general 
definite  direction  at  more  or  less  regular  periodic  times.  So  birds  mi- 
grate northward  with  the  advance  of  warm  weather;  some  fish  migrate 


THE  PALEONTOLOGIC  RECORD      ~  31 

from  sea  up  rivers  in  breeding  seasons;  pigeons  fly  eastward  or  west- 
ward in  great  flocks,  or  grasshoppers  invade  a  rich  country  devouring 
the  vegetation  in  their  path,  or  lemmings  migrate  across  country  in 
great  quantities. 

The  term  in  these  cases  has  to  do  with  movements  of  one  kind  of 
animal  in  relation  to  the  comparatively  stable  range  of  feeding-ground 
for  the  remainder  of  the  fauna  inhabiting  the  areas  concerned.  The 
term  is  rarely  if  ever  applied  to  the  slower  movement  of  the  whole  body 
of  animals  of  a  fauna,  coincident  with  great  changes  of  climate,  such 
as  the  advance  of  the  glacial  cover  over  the  northern  parts  of  Europe 
or  America  produced  during  the  glacial  age,  or  the  advance  of  an 
Asiatic  fauna  across  the  Bering  Straits  and  down  the  west  coast  of 
North  America  at  some  Pleistocene  time  when  an  ice  bridge  furnished 
means  of  communication  by  land  from  one  continent  to  the  other. 
Perhaps  there  is  no  impropriety  in  extending  the  application  of  the 
term  migration  to  these  latter  cases  in  which  the  whole  fauna  and 
flora  of  a  region  is  affected  instead  of  single  or  a  few  species;  and  in 
which  the  change  of  position  of  habitat  is  slow  and  spread  over  a  great 
period  of  time  instead  of  being  coincident  with  annual  change  of  sea- 
sons. The  term  may  equally  well  be  applied  to  movements  in  the 
seas  and  movements  on  the  lands. 

There  is,  however,  one  reason  for  choosing  a  separate  name  for  the 
movements  of  the  latter  kind  to  distinguish  their,  from  typical  migra- 
tions. 

In  the  first  class  of  cases  the  migration  is  voluntary  and  is  per- 
formed by  those  organisms  which  have  the  power  of  more  or  less  rapid 
locomotion.  They  may  be  said  to  do*  the  migrating  themselves.  In 
the  second  case  the  movements  are ./  involuntary  and  the  movement  is 
forced  upon  all  the  living  organises  of  the  region  and  the  change  in 
position  may  be  supposed  to  take  place  by  the  contracting  on  one  side 
of  the  area  of  the  conditions  of  possible  existence  for  the  species  and 
the  extension  on  the  other  side  c>f  favorable  conditions  of  environment. 
The  movements  extend  over  marjy  generations  of  life  so  that  relatively 
sedentary  species  may  gradually  -adjust  their  locus  hdbitans  to  a  given 
direction  of  migration.  To  this  letter  process  of  migration  I  have  been 
accustomed  to  apply  the  term  "  shifting  of  faunas." 

Migration  of  species  is  an  expression  of  the  ability  of  some  organ- 
isms to  appreciate  slight  changes  o^  favorable  conditions  of  environ- 
ment and  to  take  advantage  of  the  letter  conditions  during  the  life- 
time of  an  individual.  Shifting  of  faunas  is  an  expression  of  the 
necessity  for  the  perpetuation  of  the  rac  a  of  certain  conditions  of  en- 
vironment and  the  dying  out  of  the  w'hole  fauna  in  the  areas  from 
which  the  favorable  conditions  are  remo  ved  with  corresponding  spread 
of  the  fauna  into  new  areas  into  whichi  the  favorable  conditions  have 
been  shifted. 


32  THE  PALEONTOLOGIC  RECORD 

Shifting  of  faunas  is  an  expression  of  the  inability  of  the  species 
of  the  fauna  to  survive  under  the  changed  conditions  of  environment 
which  have  overwhelmed  them  in  the  original  habitat;  but  of  an  abil- 
ity on  the  part  of  all  those  which  migrate  to  follow  the  favorable  con- 
ditions as  they  shift  from  one  area  to  another. 

In  both  typical  migration  of  species  and  shifting  of  faunas  change 
in  the  environmental  conditions  of  life  constitute  the  stimulus  to  change 
of  habitat  on  the  part  of  the  organisms;  and  the  movement  of  the  or- 
ganisms is  a  direct  response  to  the  stimulus — those  organisms  in  the 
first  case  which  migrate  showing  their  greater  vitality  compared  with 
their  neighbors  who  stay  at  home;  while  those  who  stay  at  home  show 
a  greater  power  of  endurance  and  organic  adjustment  to  wider  range 
of  environmental  conditions. 

In  the  case  of  the  shifting  faunas  those  which  endure  without 
change  of  characters  exhibit  an  acquired  closeness  of  adjustment  to 
some  particular  combination  of  environmental  conditions  which  they 
are  forced  to  follow  or  die  and  suffer  annihilation.  The  evidence  of 
their  endurance  is  indicated  by  return  and  reoccupation  of  the  same 
area  at  a  later  geological  stage  when  by  their  reappearance,  the  orig- 
inal condition  of  environment  may  be  assumed  to  have  recurred. 

In  the  case  of  living  organisms  evidence  of  migration  is  found  in 
the  actual  presence  of  the  species  at  one  time  in  a  region  at  a  consider- 
able distance  from  its  ordinary  locus  hdbitans;  and  in  some  cases  by  see- 
ing the  species  in  the  process  of  migration,  as  for  instance  the  temporary 
alighting  in  fatigued  condition  of  flocks  of  northern  land  birds  on 
Bermuda  Island  on  their  migration  southward. 

In  the  case  of  fossil  species  the  shifting  of  a  fauna  is  expressed  by 
the  presence  of  a  number  of  species  representing  an  earlier  fauna  in  a 
stratum  in  the  midst  of  rocks  containing  a  different  and  dominantly 
later  set  of  species. 

The  fauna  is  then  said  to  recur  and  it  is  the  recurrence  of  the 
fauna  which  forms  the  basis  for  the  inference  that  the  fauna  has 
shifted  its  locus  liabitans  during  the  period  of  time  represented  by  the 
sedimentary  deposits  separating  the  formation  in  which  the  fauna  is 
dominant  from  the  zone  in  the  higher  formation  in  which  the  recur- 
rent species  are  found. 

This  theory  of  the  shifting  of  place  and  the  recurrence  in  time  of 
the  same  fauna  involves  certain  conceptions  as  to  the  nature  of  species 
and  the  laws  of  evolution  which  it  is  important  to  consider. 

§  9.  Evidence  of  Continuity. — To  establish  evidence  of  motion  in 
migration  as  in  any  other  kind  of  motion  it  is  all  important  to  know 
that  the  body  or  bodies  to  which  the  motion  is  ascribed  is  continuously 
the  same. 

In  the  Devonian  case  I  have  been  studying  the  moving  body  is  a 


THE  PALEONTOLOGIC  RECORD  33 

fauna;  not  only  have  I  found  it  necessary  to  establish  identity  of  the 
species  in  the  recurrent  zones  with  those  of  the  initial  zones,  but  it  is 
essential  to  show  that  the  faunas  as  a  whole  are  the  same. 

To  put  this  in  another  form  of  statement  we  must  establish  the  fact 
that  not  only  the  individual  species  have  retained  their  specific  char- 
acters,  but  the  further  fact  that  the  equilibrium  of  adjustment  to  each 
other  in  the  faunal  community  has  not  been  changed,  in  order  to  prove 
that  the  recurrent  fauna  is  the  direct  successor  of  a  fauna  represented 
in  the  rocks  at  a  lower  horizon. 

This  has  led  to  such  distinction  as  rare  and  dominant  species  of  the 
fauna,  and  only  as  some  such  comparative  frequency  of  the  species  in 
the  faunal  combination  is  apparent  can  we  be  sure  that  we  are  not 
considering  an  accidentally  accumulated  sample  of  a  general  fauna. 

The  presence  of  occasional  associated  species  belonging  to  the 
normal  fauna  of  the  formation  in  which  the  recurrent  zone  appears  is 
not  antagonistic  to  the  theory,  because  the  theory  proposes'  an  invading 
of  the  territory  occupied  by  the  normal  fauna,  and  whatever  were  the 
causes  which  brought  about  the  shifting  of  the  fauna  they  were  not 
so  completely  different  as  to  annihilate  all  evidence  of  the  fauna  previ- 
ously occupying  the  ground.  Hence  it  is  only  necessary  to  find  an 
abrupt  change  of  the  grand  majority  of  species  to  make  the  induction 
that  the  faunas  have  shifted  their  habitat. 

The  theory  involves  the  further  conception  of  grand  general  faunas 
which  have  their  center  of  habitat  and  distribution  in  permanent 
oceanic  basins,  as  distinguished  from  the  special  and  (in  geological 
strata)  temporarily  expressed  faunas  such  as  we  are  accustomed  to  as- 
sociate with  individual  geologic  formations. 

In  the  case  before  us  two  such  general  faunas  are  in  evidence,  one 
of  which  in  its  dominant  characteristics  is  traced  westward  into  Iowa, 
Idaho  and  Arizona  and  up  the  Mackenzie  Eiver  valley  to  the  north  and 
across  the  polar  regions  to  Russia  and  northern  Europe.  The  other 
is  traced  eastward  and  southward  into  central  and  southern  Europe 
and  also  dominantly  into  South  America. 

Although,  with  our  present  knowledge,  it  is  not  possible  to  deter- 
mine in  any  temporary  expression  of  marine  faunas  those  particular 
species  which  were  derived  from  one  from  those  derived  from  the  other 
grand  source,  it  is  possible  to  recognize  numerous  species  which  belong 
to  one  center  of  distribution  and  others  that  belong  normally  to  the 
other. 

§10.  Interpretation  of  the  Facts. — It  is  also  important  to  keep  our 
heads  clear  in  interpreting  the  facts. 

It  is  only  by  close  examination  and  comparison  of  the  fossils  them- 
selves that  identity  of  species  or  identity  of  faunas  can  be  established. 

The  fixed  characters  of  species  are  not  only  the  characters  by  which 


34  THE  PALEONTOLOGIC  RECORD 

one  species  is  distinguished  from  another,  but  they  are  of  generic, 
ordinal  and  even  class  value,  and  they  may  be  of  immense  age  in  the 
race  and  mark  no  special,  narrow  stage  of  its  history. 

It  is  a  question  of  interpretation  whether  each  particular  phase  of 
expression  of  fluctuating  characters  is  a  matter  of  time  or  of  environ- 
ment. 

I  have  reached  the  conclusion  that  it  is  those  species  which  have 
the  greater  degree  of  normal  and  persistent  fluctuation  of  character 
which  migrate  and  follow  the  shifting  conditions  of  environment,  and 
their  life  period  is  correspondingly  longer. 

On  the  other  hand  species  whose  plasticity  of  characters  is  narrow, 
are  more  closely  adjusted  to  their  environment,  are  local  in  their  range 
of  habitat,  and  temporary  in  their  geological  life-period. 

Interpreting  the  facts  on  this  basis  it  is  the  phases  of  continuously 
fluctuating  characters  in  species  of  wide  geographic  distribution  and 
long  geologic  range  which  furnish  the  most  satisfactory  evidence  of 
temporary  stages  in  the  life  history  of  faunas. 

Another  question  of  interpretation  arises  when  we  attempt  to  re- 
construct the  physical  condition  of  the  environment  at  successive 
stages  of  time. 

In  a  single  vertical  section  we  have  positive  evidence  of  succession 
in  time.  If  we  were  sure  that  no  recurrence  of  the  same  fauna  could 
take  place  we  could  correlate  two  vertical  sections  strictly  upon  the 
fauna  contained  in  the  strata,  on  the  basis  of  the  supposition  that  the 
single  fauna  appeared  but  once  in  the  section  and  that  when  it  ceased 
in  a  given  section  its  whole  life  period  was  expressed.  But  the  facts 
show  us  that  this  is  not  the  case  in  nature.  In  geological  times  as  in 
the  present,  we  know  that  many  distinct  faunas  are  living  on  the  face 
of  the  earth  at  the  same-  time,  even  for  very  similar  conditions  of  en- 
vironment. It  becomes  therefore  a  very  complex  matter  to  correlate 
two  sections  in  which  the  order  of  faunas  and  the  character  of  the 
sediments  differ;  which  is  generally  the  case  for  any  two  sections  sepa- 
rated by  fifty  miles  from  each  other,  although  on  stratigraphic  evi- 
dence they  may  be  properly  interpreted  as  covering  the  same  interval 
of  time. 

PALEONTOLOGIC  EVIDENCES  OF  ADAPTIVE  EADIATION 

BY  PROFESSOR  HENRY  FAIRPIELD  OSBORN 

AMERICAN     MUSEUM     OF     NATURAL     HISTORY 

rjlHE  law  of  adaptive  radiation1  is  an  application  of  paleontology 
-•-  of  the  idea  of  divergent  evolution  as  conceived  and  developed 
successively  in  the  studies  of  Lamarck,  Darwin,  Huxley  and  Cope.  It 

1  Osborn,  H.  F.,  "  The  Law  of  Adaptive  Radiation,"  Amer.  Naturalist,  Vol. 
XXXVI.,  No.  425,  pp.  353-363. 


THE  PALEONTOLOGIC  RECORD 


35 


is  more  than  divergence  because  it  implies  evolution  in  every  direction 
from  a  central  form.  The  idea  of  radii,  or  radiations  from  a  central 
form  greatly  assists  the  imagination,  because  a  distinctive  feature  of 
paleontology  is  that  we  are  constantly  dealing  with  fragments  of  his- 
tory. The  radiations  which  have  been  discovered  must  be  supple- 
mented by  those  which  remain  to  be  discovered,  and  it  is  very  remark- 
able how  in  group  after  group  of  animals  these  missing  "  radii "  have 
turned  up. 

Eadiation  actually  begins  in  certain  single  organs,  and  the  first 
principle  to  be  observed,  as  shown  in  the  accompanying  diagram,  is 


LIMBS  AND  FEET 


VOLANT 


FOSSORIAL 


ARBOREAL 


Short-limbed,  plantigrade,  1  AMBULATORY 
pentadactyl,  unguicu-  I  OB 

late  Stem  J  TERRESTRIAL 


NATATORIAL 
Amphibious 


CURSORIAL 
Digit  igrade 


Aquatic 


Unguligrade 


TEETH 

OMNIVOROUS 


(Fish 
Flesh 
Carrion 


HERBIVOROUS  ^ 


Grass 

Herb 

Shrub 

Fruit 

Root 

MYRMECOPHAGOUS 
Dentition  reduced 

Stem  INSECTIVOROUS 
MAIN  LIKES  OF  ADAPTIVE  RADIATION  OF  (a)  limbs  and  feet,  (6)  teeth  among  mammals. 


36  THE  PALEONTOLOGIC  RECORD 

that  radiation  of  different  parts  of  the  body  is  not  necessarily  cor- 
related ;  that  is,  that  the  adaptive  divergence  of  the  feet  and  limbs  may 
take  one  direction,  while  that  of  the  teeth  and  skull  may  take  another 
direction.  Thus  great  variety  in  combinations  of  characters  may  arise, 
bringing  about  the  very  antithesis  of  Cuvier's  supposed  "law  of  cor- 
relation " ;  for  we  find  that  while  the  end  results  of  adaptation  are  such 
'that  all  parts  of  an  animal  conspire  to  make  the  whole  adaptive,  there 
is  no  fixed  correlation  either  in  the  form  or  rate  of  development  of 
parts,  and  that  it  is,  therefore,  impossible  for  the  paleontologist  to 
predict  the  anatomy  of  an  unknown  animal  from  one  of  its  parts  only, 
unless  the  animal  happen  to  belong  to  a  type  generally  familiar.  For 
example,  among  the  land  vertebrates  the  feet,  which  are  associated  with 
the  structure  of  the  limbs  and  trunk,  may  take  one  of  many  lines  of 
adaptation  to  different  media  or  habitats,  either  aquatic,  terrestrial, 
arboreal  or  aerial;  while  the  teeth,  which  are  associated  with  the  struc- 
ture of  the  skull  and  jaws,  also  may  take  one  of  many  lines  of  adapta- 
tion to  different  kinds  of  food  or  modes  of  feeding,  whether  herbivorous, 
insectivorous  or  carnivorous.  Through  this  independent  adaptation  of 
different  parts  of  animals  to  their  specific  ends  there  have  arisen  among 
vertebrates  almost  unlimited  numbers  of  combinations  of  food  and  tooth 
structure. 

Alternations  of  Habitat. — In  the  long  vicissitudes  of  time  and 
procession  of  continental  changes  animals  have  been  subjected  to  alter- 
nations of  habitat  either  through  their  own  migrations  or  through  the 
"migration  of  the  environment  itself,"  to  employ  Van  den  Broeck's 
epigrammatic  description  of  the  profound  and  sometimes  sudden  en- 
vironmental changes  which  may  take  place  in  a  single  locality.  The 
traces  of  alternations  of  anatomical  adaptation  corresponding  with 
these  alternations  of  habitat  are  recorded  both  in  paleontology  and 
anatomy.  For  example,  Huxley  in  1880  briefly  suggested  the  arboreal 
origin  of  all  the  marsupials,  a  suggestion  which  has  been  confirmed 
abundantly  by  the  detailed  studies  of  Dollo  and  Bensley,  according  to 
which  we  may  imagine  that  the  marsupials  have  passed  through  a  series 
of  phases,  as  follows:  (1)  a  very  early  "terrestrial  or  ambulatory" 
phase,  (2)  a  "primary  arboreal"  phase  as  exemplified  by  the  tree 
phalangers  of  the  present  day,  (3)  a  "secondary  terrestrial"  phase 
as  exemplified  by  the  kangaroos  and  wallabies,  (4)  a  "  secondary  ar- 
boreal "  phase  as  exemplified  by  the  tree  kangaroos. 

Each  one  of  these  phases  has  left  its  anatomical  record  in  the  struc- 
ture of  the  feet  and  limbs,  although  this  record  is  often  obscured  by 
adaptation. 

Louis  Dollo  especially  has  contributed  most  brilliant  discussions  of 
this  theory  of  "alternations  of  habitat"  as  applied  not  only  to  the 
interpretation  of  the  anatomy  of  the  marsupials  but  of  many  kinds  of 


THE  PALEONTOLOGIC  RECORD  37 

fishes,  and  to  such  reptiles  as  the  herbivorous  dinosaurs  of  the  Upper 
Cretaceous. 

This  brief  consideration  of  the  external  features  of  adaptation  leads 
us  to  glance  at  groups  of  animals.  We  here  observe  the  influence  of 
geographic  distribution;  we  observe  the  adaptive  radiation  of  groups 
botfa  continental  and  local. 

Continental  Adaptive  Radiation. — Among  the  Tertiary  mammals 
we  can  actually  trace  the  giving  off  of  radii  in  several,  sometimes  in  all, 
directions  for  the  purpose  of  taking  advantage  of  every  opportunity  to 
secure  food,  to  escape  enemies,  and  to  reproduce  kind,  the  three  phe- 
nomena of  the  struggle  for  existence.  Among  such  well-known  quad- 
rupeds as  the  horses,  rhinoceroses  and  titanotheres  the  modifications 
involved  in  these  radiations  can  be  clearly  traced.  Thus  the  history  of 
the  life  of  continents  presents  a  picture  of  contemporaneous  radiations 
in  different  parts  of  the  world.  We  observe  the  contemporaneous  and 
largely  independent  radiations  of  the  hoofed  animals  in  South  America, 
in  Africa  and  in  the  great  continent  comprising  Europe,  Asia  and 
North  America. 

Through  the  laws  of  parallelism  and  convergence  each  of  these 
radiations  produced  a  greater  or  less  number  of  analogous  groups. 

While  originally  independent,  the  animals  thus  evolved  separately  as 
autochthonous  types  in  many  cases  finally  mingled  together  as  migrant 
or  invading  types. 

We  may  thus  work  out  gradually  the  separate  contributions  of  the 
great  land  masses  of  North  America,  South  America,  etc.,  to  the  mam- 
malian fauna  of  the  world.  As  a  rule  the  greater  the  continents  the 
more  important  and  fundamental  the  orders  or  larger  groups  of  mam- 
mals which  have  radiated  in  them;  the  lesser  land  masses  and  conti- 
nental islands,  like  Australia,  have  been  less  favorable  to  wide  adaptive 
radiation.  One  of  the  most  interesting  features  of  adaptive  radiation  is 
that  it  may  also  occur  locally. 

Local  Adaptive  Radiation. — On  a  smaller  scale  are  the  local  adaptive 
radiations  which  occur  through  segregation  of  habit  and  local  isolation 
in  the  same  general  geographic  region  wherever  physiographic  and 
climatic  differences  are  sufficiently  great  to  produce  local  differences  in 
food  supply  or  other  local  factors  of  change.  This  principle  is  well 
known  among  living  animals,  and  it  is  now  being  demonstrated  among 
many  of  the  Tertiary  mammals,  remains  of  four  or  five  distinct  genetic 
series  having  been  discovered  in  the  same  geologic  deposits. 

The  existence  of  multiple  phyla  of  related  animals,  as  of  the  rhi- 
noceroses, horses  and  titanotheres  in  the  same  localities  is  due  partly 
to  the  operation  of  the  law  of  local  adaptive  radiation. 

This  is  conspicuously  the  case  among  the  titanotheres,  for  example, 
the  chief  evolution  of  which  can  be  traced  in  the  Eocky  Mountain 


38  THE  PALEONTOLOGIC  RECORD 

region.  In  the  Eocene  we  discover  four  or  five  independent  local 
phyla;  again  in  the  Oligocene  we  discover  five  or  six  independent  local 
phyla.  The  evolution  of  these  animals  appears  to  have  been  chiefly 
American. 

In  other  cases,  however,  the  polyphyletic  condition  appears  to  have 
been  through  the  mingling  with  local  phyla  of  phyla  evolved  in  other 
countries.  This  is  illustrated  in  the  case  of  the  Middle  Miocene  rhi- 
noceroses of  America,  which  are  invaded  by  rhinoceroses  of  Eurasiatic 
or  European  origin. 

In  studying  the  herbivorous  quadrupeds,  therefore,  we  must  keep 
in  the  imagination  constantly  the  production  of  local  phyla  through 
local  radiation  and  the  intermingling  of  foreign  phyla  through  migra- 
tion. There  are  a  few  very  striking  and  profound  differences  between 
quadrupeds  which  recur  so  frequently  that  where  we  discover  one  form 
we  may  surely  anticipate  the  discovery  of  the  opposite  or  antithetic 
form:  in  other  words,  there  are  extremes  of  structure  shown  in  the 
proportions  of  the  skull,  of  the  teeth,  of  the  limbs,  and  groups  of 
quadrupeds  are  constantly  tending  through  adaptive  radiation  to  reach 
these  extremes.  Some  of  the  contrasting  extremes  are  the  following: 
brachyodonty  vs.  hypsodonty,  dolichocephaly  vs.  brachycephaly,  dolicho- 
pody  vs.  brachypody. 

For  example,  a  local  adaptive  radiation  observed  in  the  horses  is 
that  the  forest-living  types  are  brachyodont,  or  possess  short-crowned 
teeth,  while  the  desert-living  horses  are  hypsodont,  typically  grazers, 
with  long-crowned  teeth. 

Extremes  of  long-headedness  and  short-headedness,  of  long-foot- 
edness  and  of  short-footedness,  comprise  a  very  large  part  of  the  mech- 
anism of  adaptive  radiation;  but  we  have  to  do  also  with  long-necked 
and  short-necked  types,  and  with  many  other  chances  of  proportion 
which  are  correlated  with  different  feeding  habits. 


THE  PALEONTOLOGIC  RECORD  39 


ANATOMY   AND    PHYSIOLOGY    IN    INVERTEBRATE    EX- 
TINCT ORGANISMS 

BY  RUDOLF  RUEDEMANN 

STATE  MUSEUM,  ALBANY,  N.  Y. 

THE  inquiry  into  the  position  of  anatomy  and  physiology  in  in- 
vertebrate paleontology  seems  very  appropriate  at  present,  since 
paleontology  is  steadily  becoming  more  closely  affiliated  to  zoology,  and 
the  sphere  of  zoology  is  at  present  dominated  by  comparative  anatomy 
and  physiology. 

Since,  however,  invertebrate  paleontology  has  only  the  hard  parts, 
mostly  outer  shells,  at  its  disposal,  the  view  still  prevailing  among 
zoologists  that  little  is  to  be  expected  from  it  in  regard  to  the  solution 
of  the  problems  of  anatomy  and  physiology  of  the  lower  animals  seems 
natural.  Nevertheless,  the  results  already  attained  prove  that  if  paleon- 
tologists do  not  approach  their  material  with  a  geological  knowledge 
only,  as  has  been  done  in  the  past  altogether  too  often,  most  gratifying 
results  may  be  obtained,  at  least  in  some  classes,  for  it  must  be  con- 
ceded that  the  connection  of  the  hard  parts  with  the  fleshy  parts  is  very 
unlike  in  different  classes;  it  is  very  intimate  in  some,  as  the  crinoids 
and  brachiopods,  and  again  more  indifferent,  as  in  the  gastropods. 

But  it  is  not  claiming  too  much  for  invertebrate  paleontology  if  we 
say  that  where  the  hard  parts  are  of  great  structural  importance, 
paleontology  has  earlier  taken  cognizance  of  this  fact  and  consequently 
gone  ahead  of  zoology.  As  an  instance  I  may  cite  Zittel's  investigations 
of  the  skeleton  of  the  hexactinellid  sponges  which  have  taught  the 
fundamental  importance  of  the  form  of  the  spicules  and  the  structure 
of  the  skeleton  in  that  class  and  whose  results  have  been  readily 
adopted  by  zoologists.  In  classes  which,  as  the  brachiopods  and  crinoids, 
are  to-day  mere  shadows  of  their  former  greatness,  paleontology  has  its 
greatest  chance,  and  it  would  fail  in  its  task  if  it  would  there  not  be- 
come the  instructor  of  the  affiliated  science;  and  it  is  gratifying  to  see 
that  this  fact  is  finding  recognition,  as,  for  instance,  in  Ray  Lankester^s 
"Treatise  of  Zoology,"  where  the  chapter  on  the  crinoids  has  been 
entrusted  to  Bather,  a  paleontologist  and  one  of  the  best  authorities  on 
crinoids. 

It  is  apparent  that  in  such  classes  as  those  just  mentioned,  of  which 
only  the  last  ends  of  the  branches  are  still  alive,  the  origin  and  nature 


40  THE  PALEONTOLOGIC  RECORD 

of  many  structures  can  not  be  elucidated,  even  by  the  embryology  and 
comparative  anatomy  of  the  recent  forms,  but  only  by  paleontology. 
Such  a  structure  is,  for  instance,  the  mystifying  stem  of  the  crinoids 
which,  by  a  study  of  the  primitive  ancestors  of  the  crinoids  among  the 
cystids,  is,  readily  recognized  as  a  dorsal  evagination  of  the  body. 
Likewise,  to  cite  another  example,  the  siphuncle  of  the  recent  Nautilus, 
which  is  obscure  as  a  wholly  rudimentary  organ,  is  in  such  primitive 
Paleozoic  cephalopods  as  Nanno  and  Piloceras,  still  seen  in  its  original 
form  and  thereby  recognized  in  its  nature. 

Since  that  which  has  already  been  accomplished  in  fossil  anatomy 
is  proof  that  there  are  still  larger  fields  to  be  ploughed  and  harvested, 
it  is  proper  to  inquire  into  the  best  methods  of  this  work  before  us. 

We  first  need  more  extensive  and  more  intensive  or  more  detailed 
purely  descriptive  anatomical  researches  of  the  invertebrate  fossils. 
There  are  many  species  that,  when  investigated  in  their  smallest  detail, 
are  bound  to  give  important  results.*  I  may  cite  here,  as  examples  of 
such  accomplishments,  Hudson's  minute  study  of  the  strange  Blas- 
toidocrinus  of  our  Chazy  rocks  with  its  90,000  ossicles,  or  that  of  the 
Eurypterus  fischeri  by  Holm.  Of  this  archaic  fossil  marine  arachnoid, 
a  relative  of  the  scorpion  and  of  the  king  crab,  it  can  be  fairly  said  that, 
as  far  as  its  chitinous  integument  is  concerned,  it  is  as  well  known  as 
any  recent  species.  "We  know,  through  Holm,  its  gills,  its  complex 
genital  appendages  of  both  sexes,  and  even  its  fine  hairs  and  bristles. 
Dr.  Clarke  and  myself  have  lately  continued  these  investigations  in 
the  American  eurypterids,  and  there  observed  the  structure  of  the  com- 
pound eyes,  the  pore  system  of  the  segments,  the  genital  apertures,  the 
mode  of  moulting,  the  arrangement  of  some  of  the  principal  muscles 
and  other  anatomical  facts  of  interest. 

It  can  be  said  that  this  field  of  detailed  descriptive  anatomy  has 
been  merely  touched  thus  far,  as  far  as  our  fossil  invertebrates  are  con- 
cerned, and  altogether  too  much  neglected.  This  is  not  only  true  as  to 
the  gross  anatomy,  but  still  more  so  as  to  the  microscopic  structure. 
It  must  be  conceded  that  owing  to  the  secondary  changes  in  the  rocks, 
this  latter  line  of  investigation  meets  with  great  obstacles  not  fully  ap- 
preciated by  the  zoologist,  and  that  it  is  only  in  its  infantile  stage  in 
some  classes.  But  the  results  obtained  by  the  microscopic  research  of 
the  Paleozoic  bryozoans  in  this  country  may  be  considered  as  a  striking 
example  of  what  persistency  and  enthusiasm  may  still  accomplish.  In 
microscopic  anatomy  of  the  fossils  the  training  of  a  geologist  is  as 
much  required  as  that  of  a  zoologist  and  the  history  of  these  investi- 
gations shows  that  a  zoologist  without  geologic  training  may  be  badly 
misled  by  the  deceptive  states  of  preservation  of  the  fossils. 

The  main  object  of  anatomical  research  is  to  result  in  comparative 
anatomy  and  to  determine  what  parts  are  fundamental  or  primary  and 


THE  PALEONTOLOGIC  RECORD  41 

what  have  undergone  modifications  due  to  functional  changes.  It  is 
obvious  that  here  invertebrate  paleontology  is  in  a  position  to  answer  a 
host  of  questions  that  could  not  be  successfully  approached  by  compar- 
ative anatomy  of  recent  forms,  by  the  direct  observation  of  successive 
changes.  Its  methods  of  investigation  have  already  been  applied  with 
wonderful  success  to  large  parts  of  our  Paleozoic  crinoids,  brachiopods, 
bryozoans  and  cephalopods.  And  I  do  not  doubt  that  the  time  has 
come  when  the  preliminary  stage  of  mere  description  of  fossils  is  passed, 
and  a  monographic  treatment  of  each  class  that  would  fully  enter  into 
the  comparative  anatomy  of  all  structures  preserved,  could  be  profitably 
undertaken. 

It  is  only  by  this  work  that  paleontology  can  hope  to  make  those 
contributions  to  philosophical  anatomy  in  revealing  the  causes  of  the 
different  structures  which  it  is  especially  fitted  and  called  upon  to 
furnish  by  its  ability  to  study  the  gradual  development  of  the  struc- 
tures. Wherever  a  class  of  fossils  has  been  thus  thoroughly  treated,  it 
has  given  a  fruitful  crop  of  new  hypotheses  and  principles,  as  is  in- 
stanced by  Hyatt's  investigation  of  the  fossil  cephalopods.  Most 
classes,  and  especially  the  corals,  echinoids  and  trilobites,  await  such 
treatment  by  competent  investigators. 

Since  physiology  is  that  branch  of  biology  that  treats  of  the  laws  of 
phenomena  of  living  organisms,  it  might  seem  hopeless  to  expect  any 
information  from  the  fossil  world.  This  is  apparently  the  more  true 
in  regard  to  the  invertebrates,  since  a  special  physiology  exists  thus  far 
only  for  men  and  the  higher  invertebrates  and  the  recent  invertebrates 
are  largely  a  virgin  field.  For  this  reason  also,  only  the  most  general 
foundations  of  comparative  physiology  have  been  laid,  and  an  inverte- 
brate fossil  physiology  would  get  as  yet  but  little  support  from  that 
side.  Moreover,  the  main  source  of  exact  information  in  recent  physi- 
ology is  the  experimental  method,  and  this  is  wholly  inapplicable  to 
the  fossil  world. 

And  yet  it  seems  to  us  that  the  empiric  method  upon  which  physi- 
ology has  so  long  flourished  promises  also  rich  fruit  in  paleontology. 
I  can  do  no  more  now  than  briefly  mention  the  problems  that  most 
readily  suggest  themselves  here.  Invertebrate  paleontology  will  be 
especially  competent  to  furnish  contributions  to  the  mechanics  of 
physiology  by  throwing  light  on  the  development  of  the  means  and 
modes  of  locomotion.  In  connection  with  this  problem  invertebrate 
paleontology  also  shows  most  clearly  the  deep-reaching  influence  of 
secondary  fixation  on  the  structure  of  the  organism,  as  in  the  case  of 
the  strange  Richtfiofenia  among  the  brachiopods  and  the  EudistaB 
among  the  lamellibranchs.  It  can  not  fail  that  the  progress  in  recent 
invertebrate  physiology  will  stimulate  inquiry  into  the  physiology  of 
the  fossils ;  and  further  that,  as  invertebrate  fossil  anatomy  progresses, 
the  data  for  such  inquiry  will  also  come  forth. 


42  THE  PALEONTOLOGIC  RECORD 

Another  problem  closely  connected  with  that  of  the  mode  of  loco- 
motion is  that  of  the  origin  of  the  organs  of  sense,  and  also  upon  this, 
as  far  as  tl^e  organs  of  seeing  at  least  are  concerned,  the  fossil  inverte- 
brates are  able  to  throw  some  light,  as  in  the  trilobites  and  eurypterids. 

Another  line  of  inquiry  is  that  of  the  mode  of  nutrition  as  recog- 
nizable by  the  appendages,  and  its  influence  upon  the  general  structure 
Under  this  heading  such  interesting  minor  problems  as  that  of  the 
origin  of  parasitism  arise  and  may  be  solved,  as  indicated  by  a  recent 
publication  as  to  the  time  of  beginning,  causes  and  gradual  changes  of 
parasitism,  to^its  very  complex  present  conditions. 

Probably  also  the  physiology  of  respiration  will  in  time  receive 
important  additions  as  far  as  the  echinoderms,  crustaceans,  scorpions 
and  eurypterids  are  concerned. 

The  widest  scope,  however,  will  have  those  problems  that  are  con- 
nected with  the  reactions  of  the  organisms  to  their  physical  and  chem- 
ical surroundings.  The  invertebrate  paleontologist  meets  forever,  in 
sight  of  the  ever-changing  faunules,  the  question,  what  exterior  influ- 
ences caused  these  changes  ?  Often  they  can  be  directly  recognized,  as 
in  the  dwarfed  faunules  of  the  Devonic  pyritiferous  Tully  limestone  or 
of  the  bituminous  Marcellus  and  Genesee  shales  or  the  eurypterid 
faunas  of  the  Salina  lagoons.  The  systematic  investigation  of  these 
reactions  through  the  series  of  formations  is  an  inviting  task. 

A  special  problem  of  singular  interest  connected  with  the  reaction 
of  the  organisms  to  the  chemical  surroundings  is  that  of  the  composi- 
tion of  the  shell  of  the  invertebrates.  There  is  good  evidence  for  the 
view  that  the  shells  were  at  first  chitinous  and  that  but  gradually  they 
became  calcareous  or  siliceous.  This  important  question  again  is 
intimately  connected  with  that  of  the  original  composition  of  the  ocean, 
and  this  line  of  inquiry  again  leads  us  to  the  highly  fascinating  paleo- 
physiological  problem,  lately  so  happily  dealt  with  by  Professor  Lane, 
as  to  the  geological  evidence  on  the  original  composition  and  origin 
of  the  vital  liquid,  the  original  body  temperature  and  the  physiological 
origin  of  the  hard  parts  of  the  invertebrates  in  general. 


CONTRIBUTIONS  TO   MORPHOLOGY   FROM 
PALEONTOLOGY 

BY  PROFESSOR  WILLIAM  BULLOCK  CLARK 

THE    JOHNS    HOPKINS     UNIVERSITY 

OUR  knowledge  of  the  morphology  both  of  the  animal  and  plant 
kingdoms  has  been  largely  extended  by  the  work  of  the  paleon- 
tologist.    Mention  needs  only  to  be  made  of  the  many  species,  genera 
and  families,  even  orders  and  classes,  established  solely  for  fossil  forms 


THE  PALEONTOLOGIC  RECORD  43 

to  show  how  much  we  owe  to  paleontology.     There  is  not  a  single  sub- 
kingdom  but  has  been  immensely  enriched  from  this  source. 

Some  of  the  fossil  species  possess  morphological  characters  so  closely 
allied,  on  the  one  hand  to  earlier,  and  on  the  other  to  later,  forms  as  to 
indicate  that  they  occupy  a  position  in  the  line  of  descent,  and  phylo- 
genetic  series  have  been  established  frequently  on  this  basis.  As  ex- 
amples we  have  the  well-known  developmental  series  of  the  horse  and 
the  camel.  Other  illustrations  may  be  found  in  the  Paludinas  of  the 
Slavonian  Pliocene  and  in  the  Planorbis  types  of  Steinheim. 

Still  other  fossil  forms  combine  in  the  same  species  several  morpho- 
logical features  which  later  become  segregated  and  characterize  different 
types.  Such  " synthetic  types"  serve  to  show  the  common  origin  of 
the  forms  in  question  if  not  their  actual  ancestors  and  have  greatly 
enlarged  our  knowledge  of  the  morphology  of  the  several  groups  in- 
volved. These  early  forms  are,  for  the  most  part,  highly  generalized, 
while  their  descendents  are  variously  specialized.  Take,  for  example, 
the  mammalian  Condylartha,  small,  generalized  TJngulata  with  an 
astragalus  shaped  almost  as  in  the  Carnivora;  or  the  reptilian  Anomo- 
dontia  with  intermediate  skeletal  characters  between  the  highest 
labyrinthodonts  and  the  lowest  mammals;  or  again,  the  early  Paleozoic 
cystoids  with  generalized  characters  in  their  calyx  plates  which  appear 
in  more  specialized  forms  in  later  crinoids  and  blastoids.  An  almost 
indefinite  number  of  such  illustrations  might  be  cited. 

Still  other  fossil  forms  present  morphological  characters  so  dif- 
ferent from  other  fossil  or  living  species  that  the  genetic  relationships 
may  not  be  determined  accurately.  Some  of  these  are  possible  of  refer- 
ence to  already  defined  orders,  while  others  present  so  many  diverse 
morphological  characters  as  to  require  the  establishment  of  new  divi- 
sions for  their  reception. 

A  survey  of  the  known  fossil  and  living  forms  shows  that  not  only 
have  old  species  constantly  become  extinct  during  the  progress  of 
geological  time,  but  new  species  have  been  as  frequently  appearing. 
This  is  equally  true  of  genera,  families,  orders  or  even  classes.  Some 
forms  have  appeared  and  disappeared,  as  the  case  may  be,  suddenly; 
others  slowly.  The  great  group  of  the  Ammonites,  for  example,  dis- 
appeared suddenly  at  the  close  of  the  Cretaceous  after  showing  many 
degenerate  characters,  while  the  Trilobites  gradually  declined  during 
late  Paleozoic  time  before  their  final  extinction.  One  of  the  most 
striking  features  in  the  developmental  history  of  plants  and  animals  is 
found  in  the  great  number  of  fossil  types  which  have  left  no  descendants. 

Both  the  animal  and  plant  kingdoms  furnish  a  wealth  of  material 
with  which  to  demonstrate  the  aid  which  paleontology  has  rendered  to 
morphology. 

The  contributions  of  invertebrate  paleontology  are  numerous  and 
striking : 


44  THE  PALEONTOLOGIC  RECORD 

The  Protozoa  afford  in  the  Carboniferous  FusulinidaB  and  in  the 
Tertiary  NummulinidaB  forms  with  very  different  morphological  char- 
acters from  those  living  to-day,  while  the  numerous  extinct  species  of 
the  Lituolidas  and  Textularidse  in  the  Cretaceous  and  of  the  Miliolidae 
and  Globigerinidag  in  the  Tertiary  have  greatly  widened  our  knowledge 
of  the  entire  subkingdom. 

The  Ccelenterata  in  the  Paleozoic  Tabulata  and  Graptoloidea  show 
types  so  different  from  living  forms  that  the  systematist  has  never 
been  able  to  satisfactorily  assign  them  to  a  position  within  the  limits 
of  the  phylum.  Many  external  and  internal  characters  appear  that  are 
quite  unknown  in  later  forms.  On  the  other  hand,  the  paleontological 
subclass  of  the  Tetracoralla  long  imperfectly  understood  is  now  re- 
garded with  a  fuller  knowledge  of  the  "morphology  as  affording  the 
probable  ancestors  of  the  later  Hexacoralla. 

The  Echinodermata  have  furnished  two  classes,  the  Cystoidea  and 
the  Blastoidea,  unknown  after  the  Paleozoic,  whose  morphology  aids 
very  materially  in  an  interpretation  of  later  and  more  highly  differen- 
tiated forms  among  the  Pelmatozoa.  Thus  the  cystoids,  which  have 
been  regarded  as  the  ancestral  type  from  which  the  crinoids  have 
sprung,  afford  forms  like  the  Camarocystites,  in  which  the  arms  are 
similar  to  those  of  the  crinoids  although  the  calyx  plates  are  irregularly 
arranged  and  thus  cystoidean  in  character.  Both  the  Asterozoa  and 
Echinozoa  are  represented  in  the  fossil  state  by  many  species  that  greatly 
widen  our  knowledge  of  the  morphology  of  this  group.  Take  for 
example,  the  Echinocystites,  regarded  as  belonging  to  the  Palechinodea 
which  has  a  valvular  pyramid  of  calcareous  anal  plates  so  highly  char- 
acteristic of  the  cystoids. 

The  Molluscoidea,  to  which  phylum  belong  the  Bryozoa  and  Brachio- 
poda,  would  be  but  imperfectly  understood  from  a  morphological  stand- 
point but  for  the  vast  number  of  fossil  forms.  The  Brachiopoda  have 
been  estimated  to  have  less  than  150  living  species,  while  probably  more 
than  6,000  fossil  species  have  been  described.  Of  the  31  families  only 
7  have  living  representatives.  We  are  dependent,  therefore,  largely  on 
the  fossil  forms  for  our  knowledge  of  the  morphology  of  this  class. 

The  Mollusca  with  their  varied  forms,  although  so  well  represented 
to-day,  have  furnished  in  the  fossil  state  one  of  the  most  interesting 
and  important  orders  in  the  animal  kingdom,  the  Ammonoidea  with 
its  5,000  and  more  species  ranging  from  the  Devonian  to  the  Cretaceous. 
Even  the  allied  Nautiloidea,  although  containing  living  forms,  attained 
its  chief  development  in  the  Paleozoic,  and  it  is  from  these  ancient  forms 
that  we  obtain  our  chief  knowledge  of  the  morphology  of  this  group 
with  their  early  straight  and  irregularly  coiled  types. 

The  Arthropoda  afford  in  the  Paleozoic  the  important  groups  of  the 
trilobites  and  euripterids,  forms  that  have  aided  greatly  in  the  inter- 


THE  PALEONTOLOGIC  RECORD  45 

pretation  of  the  entire  phylum.  The  trilobites  from  their  morpholog- 
ical features  have  been  generally  regarded  as  entomostracous  crusta- 
ceans with  relationships  on  the  one  hand  to  the  Phyllopoda  and  on  the 
other  to  the  Merostomata,  while  the  coalescing  of  the  caudal  segments 
suggests  also  a  relationship  to  the  Isopoda. 

Vertebrate  paleontology  has  also  furnished  much  to  morphology. 

The  Fishes  would  be  but  imperfectly  known  in  their  wonderful 
variety  but  far  the  fossil  types.  The  problematical  group  Agnatha 
found  only  in  the  Silurian  and  Devonian  affords  no  certain  evidence 
of  a  lower  jaw  or  paired  limbs,,  and  in  some  of  the  genera  of  the  Ostra- 
coderma  mimic  in  a  curious  way  the  contemporaneous  euripterids, 
which  has  led  some  to  erroneously  ally  them  with  the  Merostomata. 
The  dermal  armor  of  most  of  these  forms  is  also  a  striking  morpholog- 
ical feature. 

Woodward  divides  the  fishes  proper  into  Elasmobranchii,  Holo- 
cephali,  Dipnoi  and  Teleostomi,  and  considers  that  the  common  an- 
cestors of  all  were  Elasmobranchs.  Numerous  fossil  forms  among  the 
Elasmobranchs  and  Dipnoids  as  well  as  the  Crossopterygians  which 
have  been  thought  by  many  to  bridge  the  gap  between  the  Telelostomi 
and  Dipnoi  have  added  largely  to  our  knowledge  of  the  phylum. 

The  Batrachians  which  consist  to-day  largely  of  diminutive  forms 
were  represented  in  the  later  Paleozoic  and  early  Mesozoic  by  the  Stego- 
cephalia  which  contain  the  giant  labyrinthodonts  with  their  highly 
complex  infolding  of  the  walls  of  the  teeth. 

The  Reptilians  which  began  their  existence  toward  the  close  of  the 
Paleozoic  became  so  numerous  and  diversified  during  the  Mesozoic  that 
this  division  of  geological  time  has  been  referred  to  as  the  age  of 
reptiles.  Several  orders  of  Saurians  containing  many  giant  types 
flourished  during  this  time,  but  became  practically  extinct  before  the 
close  of  the  period.  With  the  adaptation  of  some  for  walking  on  their 
hind  legs,  of  others  for  swimming,  and  still  others  for  flight  we  have 
developed  a  great  variety  of  morphological  features  that  would  never 
have  been  suspected  from  a  study  of  living  forms. 

The  Birds  which  are  recognized  as  possessing  certain  dinosaurian 
relationships  and  were  doubtless  derived  from  one  of  the  reptilian  orders 
are  unknown  prior  to  the  Jurassic.  The  Mesozoic  forms  are  general- 
ized, the  tail  at  first  not  being  atrophied  and  the  pelvis  imperfectly 
developed  as  in  later  forms.  The  vertebras  also  had  not  acquired  their 
saddle-shaped  articulation  while  teeth  were  present  in  the  jaws  of  the 
adults.  Such  forms  certainly  add  greatly  to  our  knowledge  of  the 
morphology  of  this  class. 

The  Mammals  which  began  in  the  early  Mesozoic  were  represented 
throughout  the  Cenozoic  time  by  highly  diversified  forms,  many  of 
which  have  left  no  descendants.  The  gradual  evolution  of  the  mam- 


46  THE  PALEONTOLOGIC  RECORD 

malian  skeleton  has  brought  about  many  morphological  modifications 
from  those  shown  in  the  Batrachia  and  Eeptilia.  We  find  the  skull 
loses  the  prefrontal  and  postfrontal  bones,  the  mandible  is  simplified, 
the  limb  bones  show  a  development  of  terminal  epiphyses  with  ossifica- 
tion to  the  center  of  the  vertebras  and  the  bones  of  the  pelvic  arch  are 
ossified.  From  the  beginning  of  the  Tertiary  time  a  marvelous  variety 
of  morphological  characters  appears,  and  without  the  fossil  types  we 
should  have  but  an  inadequate  conception  of  this  great  phylum. 

The  contributions  of  paleobotany  to  morphology  are  in  some  re- 
spects quite  as  striking  as  those  of  paleozoology. 

The  fossil  Thallophytes  have  not  furnished  any  very  striking  varia- 
tions from  their  present  morphological  features,  while  the  Bryophytes 
are  scarcely  represented  as  fossils  except  in  very  recent  deposits. 

The  remaining  phyla,  the  Pteridospermatophytes,  the  Pteridophytes 
and  the  Spermatophytes  have  their  oldest  known  beginnings  as  far 
back  as  the  Devonian  and  their  study  has  enormously  widened  the 
bounds  of  plant  morphology. 

The  Pteridospermatophytes,  which  are  confined  to  the  Paleozoic, 
are  in  habit  and  vegetative  morphology  ferns — in  methods  of  repro- 
duction and  in  the  morphology  of  their  reproductive  organs  typical  seed 
plants.  They  alter  our  whole  conception  of  ferns  and  seed  plants  and 
in  their  significance  are  comparable  to  archetypal  vertebrata,  the  acqui- 
sition of  the  seed  habit  in  plants  and  the  vertebral  column  in  animals 
probably  marking  the  culmination  of  the  transfer  of  vital  activity  from 
aquatic  to  terrestrial  conditions. 

In  the  Pteridophytes  the  extinct  Paleozoic  class,  the  Sphenophyllales, 
is  significant,  since  the  morphology  of  the  distinct  lycopod  and  Equi- 
setum  lines  seems  to  merge  in  this  group.  The  lycopod  type,  itself 
represented  in  the  existing  flora  by  six  or  seven  genera  of  herbaceous 
plants,  monotonously  uniform  in  their  morphology,  is  found  in  the 
Paleozoic  to  constitute  one  of  the  chief  units  in  the  arborescent  flora 
with  numerous  species  of  complex  organization,  whose  stem,  foliar  and 
reproductive  morphology  was  quite  unknown  to  botanists  (Lepido- 
dendron,  Sigillaria,  etc.).  The  Equisetum  type  furnishes  a  like 
case.  With  few  existing  species  of  minor  importance  and  uniform 
morphology  we  find  in  the  Paleozoic  a  host  of  forms,  many  of  them 
arborescent  and  of  varied  and  complex  structure  (Catamites,  Archceo- 
calamites,  etc.).  Similar  examples  could  be  drawn  from  the  fossil 
representatives  of  the  true  ferns. 

In  the  Spermatophytes  another  wholly  extinct  class,  the  Cordaitales, 
embraces  a  curiously  organized  group  of  conifers  extending  back  to  the 
oldest  horizons  from  which  land  plants  are  found,  and  continuing  to 
the  close  of  the  Paleozoic  as  one  of  the  most  abundant  as  well  as  the 
highest  type  of  pre-Mesozoic  r>lant.  In  the  older  Mesozoic  we  find  t\TO 


THE  PALEONTOLOGIC  RECORD  47 

groups  of  plants  which  have  made  similar  great  contributions  to 
morphology.  The  Cycadales  or  cycad-like  plants,  which  to-day  are  an 
inconspicuous  group,  were  one  of  the  dominant  Mesozoic  types,  and  any 
understanding  of  the  modern  forms  rests  entirely  upon  a  study  of  their 
immensely  abundant  Mesozoic  ancestors.  The  other  group,  the  Gink- 
goales,  represented  in  the  existing  flora  by  a  single  species,  the  ginkgo, 
is  found  in  the  Mesozoic  to  have  been  represented  by  many  genera  and 
species  of  great  diversity. 

The  dominant  plants  of  to-day,  the  conifers  on  the  one  hand,  and 
the  angiosperms  on  the  other,  have  each  afforded  many  extinct  genera, 
the  former  with  more  fossil  than  recent  species,  and  only  understand- 
able in  the  light  of  their  fossil  ancestors.  Vegetable  morphology  based 
only  upon  existing  plants  abundantly  demonstrated  its  sterility  before 
the  relative  recent  study  of  fossil  plants  placed  it  upon  an  altogether 
new  basis. 

EELATION   OF   EMBEYOLOGY  AND   VBETEBEATE 
PALEONTOLOGY 

BY  PBOFESSOB  RICHARD  SWANN  LULL 

UNIVERSITY 


THE  problem  of  recapitulation  among  vertebrates  gives  by  no  means 
as  accurate  results  as  among  invertebrate  forms,  for  while  a  single 
adult  shell,  if  perfectly  preserved,  will  often  display  the  entire  life 
history  or  ontogeny  of  the  individual,  a  bone,  or  even  a  ^complete 
skeleton,  is  rarely  retrospective  and  if  at  all  only  in  some  minor  detail. 
The  vertebratist,  therefore,  in  his  study  of  ontogeny,  for  comparison 
with  racial  history  must  needs  follow  either  the  entire  growth  of  one 
animal,  a  thing  manifestly  impossible  when  the  embryonic  stages  are 
considered,  or  study  a  long  series  of  individuals  in  various  stages  of  de- 
velopment, the  securing  of  which  in  the  great  majority  of  cases  is  largely 
the  result  of  a  number  of  happy  accidents.  When  one  comes  to  weigh 
the  evidence  offered  by  the  actual  embryos  of  fossil  vertebrates  he  will 
find  a  very  great  dearth  of  material,  for  fossil  embryos  —  that  is,  the 
stages  in  the  life  history  before  birth  or  hatching  —  are  extremely  rare. 
Eecent  embryology,  on  the  other  hand,  is  more  productive  of  results 
and  the  earlier  stages  of  certain  organs  often  suggest  those  of  equivalent 
development  in  animals  of  the  past.  In  his  interpretation  of  a  given 
structure,  however,  one  has  to  bear  in  mind  whether  it  may  not  have 
been  modified  to  suit  some  modern  need  in  the  life  history  of  the  indi- 
vidual, and  thus  no  longer  give  us  a  true  image  of  bygone  structure. 
These  coenogenetic  organs  are  not  historic,  but  as  Wilder  says,  "  have 
to  do  with  such  immediate  environmental  problems  as  nutrition  or 
protection."  Again,  if  the  organ  has  approximately  the  same  form 


48  THE  PALEONTOLOGIC  RECORD 

and  character  in  the  ancestral  type  at  the  same  stage  of  its  development, 
it  represents  an  actual  repetition  of  past  history  and  is  therefore  palm- 
genetic.  Sometimes  it  is  not  quite  clear,  however,  under  which  caption 
the  embryonic  structure  comes,  and  its  interpretation  must  be  attempted 
with  caution. 

0  shorn  in  his  lectures  to  his  students  speaks  of  the  three-fold  evi- 
dence for  evolution  which  stands  firmly  like  a  tripod,  the  legs  of  which 
are  comparative  anatomy,  embryology  and  paleontology;  and  the  evi- 
dence of  each  should  correspond,  provided  the  interpretation  be  correct. 
Of  these,  however,  embryology  is  manifestly  the  weakest  member,  while 
paleontology  is  a  tower  of  strength ! 

The  reptiles  are  so  rare  as  embryos  and  withal  so  ancient  a  group 
that  their  ontogeny  throws  but  little  light  upon  paleontology.  Among 
the  fossil  forms  a  number  of  specimens  of  Ichthyosaurus  have  been 
found  with  young  contained  within  the  body  of  the  adult.  Many  of 
these  are  in  the  normal  position  for  f ceti-in-utero ;  others  are  displaced, 
with  the  head  directed  forward.  These  latter  Branca  thinks  may  be 
young  that  have  been  eaten.  There  is  also,  at  times,  a  very  great 
difference  in  the  size  of  the  contained  young.  Aside  from  a  slight  dif- 
ference in  proportions,  especially  that  of  head  to  trunk,  and  a  less  degree 
of  hardness  of  the  embryonic  bones,  as  indicated  by  their  being  crushed 
over  the  parent's  ribs,  the  young  teach  us  nothing  as  to  ancestral  struc- 
ture as  they  are  in  every  way  perfect  ichthyosaurs.  They  do  prove, 
however,  when  the  evidence  of  viviparity  which  they  offer  is  taken  in 
connection  with  the  supreme  degree  of  aquatic  adaptation  indicated, 
that  the  ichthyosaurs  were  high  sea-forms,  never  coming  ashore  even 
for  egg-laying. 

That  certain  of  the  dinosaurs  were  also  viviparous  may  be  proved 
by  an  embryo  contained  in  the  unique  specimen  of  Compsognathus 
longipes  from  the  Jurassic  of  Bavaria.  So  far  as  I  am  aware  this 
embryo  gives  no  other  evidence  of  ontogenetic  value. 

The  turtles  have  been  made  the  subject  of  exhaustive  study  by  Hay 
and  from  the  embryological  point  of  view  by  Clark  under  L.  Agassiz. 
Anatomically  they  are  the  most  remarkable  of  reptiles,  having  under- 
gone during  their  career  an  extreme  modification  in  many  directions 
while  retaining  a  number  of  very  primitive  characters.  The  most 
remarkable  feature  is  the  development  of  the  shield  or  carapace,  which 
contains  what  are  generally  considered  as  the  homologues  of  the  ribs  of 
other  vertebrates,  but,  strangely  enough,  here  lying  outside  of  the 
shoulder  girdle,  a  feature  wherein  the  turtles  are  utterly  unique.  The 
embryology,  which  is  well  known,  ought  to  throw  some  light  upon  the 
origin  of  this  important  feature.  In  their  earlier  stages  of  develop- 
ment the  Chelonia  resemble  the  Lacertilia,  the  chief  pecularity  being 
caused  by  the  development  of  this  carapace  which  appears  in  the  form 


THE  PALEONTOLOGIC  RECORD  49 

of  two  longitudinal  folds  extending  above  the  line  of  insertion  of  the 
fore-  and  hind-limbs  which  have  already  made  their  appearance.  Hence 
the  carapace  grows  outward  and  over  the  limb-girdles  which  come  to  lie 
within  the  rib-like  osseous  supports.  This  ontogeny  shows  us  clearly 
how  the  ancestral  carapace  may  have  been  formed.  Paleontology  has 
not  as  yet  confirmed  this,  but  doubtless  will  do  so. 

<  Among  birds  one  of  the  most  interesting  features  is  the  occurrence 
of  vestigial  tooth  papillae  in  the  jaws  of  certain  embryo  parrots  and  owls 
— reminiscent  of  Mesozoic  days  when  birds  were  toothed  in  their  adult 
state. 

Mammalian  evidence  is  very  striking  in  many  details  and  much  of 
it  has  recently  been  summarized  by  Hubrecht,  who  makes  much  of  the 
character  of  the  placentation  and  derives  from  it  and  other  features 
some  remarkable  conclusions.  Hubrecht  abandons  the  idea  of  the 
derivation  of  the  mammalia  from  the  reptilian-insectivorean  stem,  but 
on  the  contrary  derives  them  from  amphibia-like  animals  of  the  Car- 
boniferous. The  character  of  the  placentation,  moreover,  places  man, 
the  Anthropomorphse  and  the  hedgehog  among  the  most  archaic  of 
living  mammalian  types,  an  idea  also  borne  out  by  comparative  anatomy 
and  one  which  paleontology  may  some  day  confirm. 

The  most  primitive  mammals,  the  Prototheria,  are  still  very  sug- 
gestive of  their  old  reptilian  ancestry  in  many  ways,  especially  in  the 
method  of  producing  the  young  inclosed  within  an  eggshell.  The  posi- 
tion of  the  Marsupials  is  surely  low  in  the  scale  of  mammalian  life, 
although  they  show  in  many  respects  remarkable  specializations.  Wilder 
compares  them  with  the  Prototheria  in  that  they  also  bring  forth  their 
young  at  a  very  early  state  of  development,  though  not  protected  by  an 
eggshell.  The  period  during  which  they  are  permanently  attached  to 
the  nipples  within  the  pouch  is  actually  post-embryonic  and  properly 
larval.  Vestiges  of  placentation  have  been  found  in  at  least  one  mar- 
supial, a  fact  which  gives  color  to  the  belief  that  in  this  respect  they 
may  be  degenerate  rather  than  primitive.  Broom  has  shown  that  the 
modern  marsupial  shoulder  girdle  passes  through  a  prototherian  stage 
implying  a  relationship  which  is  strongly  supported  in  other  ways. 

The  foetal  Sirenia  and  Cetacea,  so  far  as  known,  show  no  greater 
development  of  hind-limbs  than  do  the  post-natal  individuals.  They 
do  show  a  marked  neck  construction  and  the  head  bent  at  right  angles 
with  the  trunk  in  a  normal  quadrupedal  posture.  The  head  of  the 
foetal  manatee  is  very  suggestive  of  the  modern  ungulate.  Eyder  has 
tried  to  prove  the  homology  of  the  caudal  flukes  in  the  Sirenia  and 
Cetacea  with  the  integument  of  the  hind  feet,  drawing  his  evidence 
largely  from  comparison  with  the  seals.  In  the  embryo  the  flukes 
appear  as  lateral  expansions  near  the  end  of  the  tail,  giving  it  a  lance- 
like  form  when  viewed  from  above.  These  flaps  by  transverse  expan- 


50  THE  PALEONTOLOGIC  RE  COED 

sion  develop  into  the  powerful  swimming  flukes  of  the  adult.  They 
may  be  compared  with  lateral  flanges  on  the  tail  of  the  sea  otter 
Enhydris,  but  in  the  latter  the  flaps  are  elongate,  while  in  the  Cetacea 
they  are  short  and  situated  toward  the  end  of  the  tail.  Nevertheless, 
the  homology  of  the  two  types  of  flange  structures  appears  true,  the 
posterior  position  and  concentration  in  the  whale  being  a  mechanical 
adaptation  which  has  become  accelerated  in  its  appearance  so  as  to  be 
embryonic.  The  presence  of  hair  on  the  body  of  the  foetal  whale  and 
of  distinct  calcareous  tooth  germs  in  both  upper  and  lower  jaws  of  the 
unborn  young  of  whalebone  whales  are  both  reminiscent. 

The  horses,  our  knowledge  of  which  is  so  complete  owing  to  the 
pioneer  work  of  Marsh  and  later  of  Osborn,  show  some  interesting 
points  of  comparison  between  foetus  and  ancestor.  The  skulls  of  pre- 
natal modern  horses  resemble  those  of  Mesohippus  or  even  of  Eohippus 
in  the  proportions  of  face  and  cranium,  the  short-crowned  grinding 
teeth,  lesser  angle  between  basi-cranial  and  basi-facial  axes  and  the  fact 
that  the  orbit  is  incompletely  ringed  with  bone.  The  feet  of  the  unborn 
foal  are  also  somewhat  reminiscent  of  old-time  conditions. 

One  of  the  most  difficult  points  to  be  reconciled  in  the  acceptance 
of  the  Cope-Osborn  theory  of  the  origin  of  molar  cusps  was  the  apparent 
non-agreement  of  cusp  ontogeny  with  the  interpreted  phylogeny  which 
this  theory  upheld.  The  difficulty  has  been  met  in  two  ways:  by  the 
supposition  that  coenogenesis  has  entered  into  the  embryogeny,  or  that 
the  paleontological  record  as  shown  by  the  trituberculists  is  open  to  a 
different  interpretation.  The  present  great  exponent  of  the  idea  claims 
that  the  matter  is  still  sub  judice  and  thus  the  problem  stands. 

In  conclusion,  the  paleontological  student  of  the  higher  vertebrates 
can  hope  to  find  in  embryology  a  host  of  valuable  suggestions,  much 
verification  of  his  work  and  sundry  apparent  inconsistencies  which  must 
in  some  way  be  reconciled.  He  should  ever  bear  in  mind  the  influence 
of  nature  and  nurture,  the  latter  often  giving  rise  to  perplexing  con- 
flicts between  the  two  records.  He  will  on  the  whole  have  in  embry- 
ology a  fair  mirror  of  the  past  wherein,  even  though  the  image  be  some- 
what distorted  and  the  more  remote  reflections  dimmed  by  time,  he  can 
view  the  striking  features  of  the  long  procession  of  the  ages. 


THE  PALEONTOLOGIC  RECORD          51 


ONTOGENY:  A  STUDY  OF  THE  VALUE  OF  YOUNG  FEA- 
TUEES  IN  DETERMINING  PHYLOGENY 


BY  PROFESSOR  F.  B.  LOOMIS 

AMHERST    COLLEGE 


IN  this  paper  I  want  to  study  what  value  is  to  be  given  to  the  prin- 
ciple that  ontogeny  is  a  brief  recapitulation  of  phylogeny,  when  it 
comes  to  the  concrete  determination  of  the  ancestry  of  a  given  genus. 
For  the  purpose  three  types  have  been  studied  carefully  and  several 
more  for  confirmations,  the  principal  study  being  between  the  young 
and  adult  of  the  pig,  cat  and  man,  the  differences  being  noted  to  see  if 
they  suggested  the  forms  considered  ancestral. 

First  let  us  consider  the  skull  of  a  six  weeks'  pig  in  comparison  with 
that  of  the  adult,  the  two  having  been  drawn  to  the  same  length.  The 
first  and  most  marked  variation  is  in  the  brain  case,  that  of  the  young 
being  relatively  vastly  larger.  The  same  is  especially  true  of  the  sense 
capsules  of  the  ear  and  eye.  The  later  growth  is  much  greater  in  those 
parts  of  the  skull  designated  as  facial,  or  having  to  do  with  the  jaws  and 
their  supports.  Then  there  is  a  change  in  the  axis  of  the  skull,  this 
being  due  to  the  growth  of  the  maxilla  region,  and  lastly  where  there 
is  any  cellular  bone  or  bone  spaces  they  are  developed  in  later  life. 
This  factor  is  especially  well  shown  in  the  development  of  the  elephant 
skull  and  in  ruminants.  It  is  coincident  with  high  crests  and  marked 
protuberances. 

While  most  of  the  features  have  been  indicated  in  the  pig,  the  same 
comparison  in  the  cat  reveals  the  same  excessive  development  of  the 
brain  case  and  sense  organs,  the  same  weakness  of  the  jaws  and  change 
in  the  axial  relations,  and  this  may  be  further  confirmed  in  looking  at 
the  contrast  between  a  three-year-old  child's  skull  and  that  of  an  adult. 

The  conclusions  then  to  be  drawn  from  this  hasty  comparison  of 
the  two  skulls  are,  first,  that  the  shape  of  the  skull  in  the  young  shows 
the  excessive  development  of  the  brain  and  sense  capsules,  so  that  the 
appearance  is  not  that  of  a  primitive  animal,  but  exactly  the  contrary, 
the  appearance  which  the  genus  would  assume  were  its  mental  or 
nervous  development  carried  to  a  much  higher  degree  than  is  the  case. 
The  embryonic  development  of  the  brain  and  sense  organs  is  pushed 
far  toward  the  beginning,  and  is  matured,  as  far  as  size  is  concerned, 
the  earliest  of  any  of  the  systems.  The  skull  is  first  an  envelope  for 
the  brain  and  sense  organs  and  is  therefore  profoundly  modified  by  this 
embryonic  peculiarity,  and  the  younger  the  individual  the  less  like  the 
adult  or  ancestor  the  skull  is  shaped. 


52  THE  PALEONTOLOGIC  RECORD 

Secondly,  the  change  of  axis  is  not  in  the  ancestral  direction,  the 
excessive  weak  condition  of  the  jaws  being  again  an  embryonic  adapta- 
tion and  not  an  ancestral  one. 

Lastly,  in  the  development  of  cancellous  tissue  is  a  condition  which 
more  nearly  approximates  the  phylogenetic  development,  but  here  even 
the  use  of  young  features  is  deceptive,  for  it  is  seldom  that  this  cellu- 
lar bone  is  developed  in  the  immediate  ancestor  but  is  rather  found  in 
several  genera  back,  being  usually  an  accompaniment  of  the  develop- 
ment of  the  heavy  facial  portion  of  the  skull.  So  much  for  form. 

Turning  to  the  dentition.  The  milk  set  of  the  pig  and  those  of  the 
adult  are  drawn  side  by  side,  and  it  is  seen  that  while  the  front  teeth 
of  the  young  approximate  those  of  the  adult,  the  comparison  is  between 
the  complicated  premolar  and  molar  sets.  Briefly,  of  the  four  pre- 
molars,  if  all  present,  in  the  young  (and  often  but  three  are  developed) 
the  two  in  front  resemble  the  premolars  to  succeed  them  in  the  perma- 
nent set,  while  the  two  rear  milk  premolars  resemble  the  permanent 
molars,  the  last  milk  premolar  being  especially  like  the  last  molar. 
This  granted,  the  interest  centers  around  whether  the  pattern  of  the 
milk  teeth  is  such  as  to  indicate  the  ancestry.  A  glance  at  the  pig  and 
its  young  will  show  that  while  the  detail  is  not  exactly  the  same  in  young 
and  old,  yet  they  are  so  alike  that  no  one  would  identify  a  single  milk 
molar  as  Hyotherium  or  any  other  suine  genus,  but  would  have  to  put 
it  in  the  genus  Sus.  Taking  other  cases  among  the  Ungulata,  the  his- 
tory of  the  naming  of  the  Miocene  genera  of  horses  gives  a  good  ex- 
ample. There  are,  according  to  Gidley,  four  genera,  Hyohippus,  Para- 
hippus,  Merychippus  and  Protohippus;  of  these,  three  were  founded  on 
young  teeth,  i.  e.,  the  first  three  named.  When  it  was  recognized  that 
they  were  young  teeth,  they  were  by  Cope  assigned  to  Protohippus,  but 
when  the  adult  teeth  were  found  it  was  clear  that  the  distinctive  features 
of  these  young  teeth  were  the  distinctive  features  of  the  adult.  For  the 
genus  Merychippus  there  is  a  difference  in  that  the  young  teeth  are  not 
cemented,  while  the  adult  are.  That  is  ancestral.  In  analyzing  the 
descriptions  of  several  genera  of  horses  usually  some  feature  can  be 
found  in  the  milk  tooth  which  is  ancestral. 

In  the  Carnivora  there  is  the  carnassial  tooth  which  is  specialized; 
in  the  upper  jaw  it  is  the  third  milk  premolar  and  the  fourth  in  the 
adult;  in  the  lower  jaw  it  is  the  fourth  milk  premolar,  and  the  first 
molar  of  the  adult.  Thus  it  is  clear  that  it  is  a  different  dental  follicle 
which  forms  the  young  and  the  adult  carnassial.  In  the  case  of  the  dog 
the  permanent  and  milk  carnassials  are  approximately  alike,  but  in  the 
case  of  the  cat  the  inner  lobe  or  protocone  occupies  a  very  different 
place  in  the  young  from  that  of  the  adult,  a  position  characteristic  of 
none  of  the  Felidae  and  suggests  some  of  the  apparently  unrelated 
Creodonts. 


THE  PALEONTOLOGIC  RECORD  53 

In  the  matter  of  the  succession  of  teeth  the  follicles  which  form  the 
last  two — the  milk  premolars — form  teeth  in  the  first  set  of  a  totally 
different  and  usually  more  advanced  character  than  the  teeth  to  be 
formed  from  the  same  follicles  in  the  permanent  set.  As  a  general 
thing  then  the  conclusion  would  be  that  the  milk  teeth  tend  to  have 
the^same  characters  as  mark  the  permanent  set,  but  when  they  vary 
they  often  retain  characters  of  the  phylogenetically  ancestral  form. 
Weber  adds  that  the  later  the  succession  the  less  the  difference  between 
the  milk  and  permanent  sets. 

Turning  to  the  limbs,  there  are  again  several  distinctly  ontogenetic 
characters,  which  are  by  no  means  ancestral.  First,  the  formation  of 
epiphyses,  so  that  a  bone  ossifies  from  three  or  more  centers.  This  is 
purely  an  ontogenetic  adaptation  and  has  no  phylogenetic  significance. 
Then  the  articular  ends  of  all  the  limb  bones  are  greatly  enlarged  as 
compared  with  adults.  This  again  is  not  phylogenetic  but  an  adapta- 
tion, the  joints  and  their  ligaments  being  early  approximated  to  their 
permanent  conditions.  Then  the  length  of  limbs  seems  to  be  ef- 
fected as  an  embryonic  adaptation.  First  take  the  case  of  man  born 
with  disproportionately  short  arms  and  legs.  The  legs  have  been  inter- 
preted as  representing  a  phylogenetic  condition,  but  the  same  rule  does 
not  apply  to  the  arms  which  were  ancestrally  long.  This  feature  of 
short  limbs  is  also  characteristic  of  carnivora  and  I  feel  that  it  is  an 
embryonic  adaptation;  certainly  the  ancestral  limb  can  not  be  deduced 
from  the  young  condition.  Quite  the  reverse  of  conditions  obtains 
among  the  Ungulata  where  the  young  at  birth  have  disproportionately 
long  limbs,  which  with  equal  certainty  does  not  represent  any  ancestral 
condition  recapitulated,  for  the  ancestral  limb  in  ancestral  forms  is 
shorter.  Again,  I  believe  the  anomalous  legs  are  adaptations  to  either 
the  necessity  for  speed  on  the  part  of  the  young,  or  for  height  to  reach 
the  teats,  suckling  being  while  the  parent  is  standing. 

In  the  cases  of  the  reduction  of  digits,  greater  portions  of  the  re- 
duced digits  are  usually  found  in  the  young  animals  than  in  the  adults, 
but  in  the  case  of  the  entire  loss  of  a  digit  it  is  also  lacking  in  the 
young  and  embryo. 

The  general  conclusion  of  the  whole  matter  would  then  be  that  the 
young  give  us  very  little  which  is  not  deceptive  in  reconstructing  an- 
cestral forms.  In  certain  cases,  namely  in  the  teeth  and  in  reduction 
of  digits,  confirmatory  points  may  be  obtained,  but  these  must  be 
used  with  care,  the  valuable  constructive  evidence  being  rather  found 
in  adult  skeletons,  and  in  morphological  comparisons.  While  allowing 
that  many  stages  are  recapitulated  in  the  development  of  an  individual, 
the  vast  number  of  adaptations  impressed  on  the  young  to  be  used  after 
birth,  make  their  skeletons  specialized  even  from  birth,  and  such  dif- 
ferences as  exist  are  seldom  reminiscent. 


54  THE  PALEONTOLOGIC  RECORD 


PALEONTOLOGY  AND   ONTOGENY 


BY  PKOFESSSOR  A.  W.  GRABAU 

COLUMBIA  UNIVERSITY 


ONTOGENY,  or  the  life  history  of  the  individual,  is  commonly 
interpreted  by  zoologists  as  its  embryology,  the  later  stages  of 
development,  from  infancy  to  old  age,  being  deemed  of  little  or  no 
importance.  This  was  the  case  fifty  years  ago;  this  is  largely  the  case 
to-day.  From  the  days  when  Agassiz  first  called  the  attention  of  zool- 
ogists to  their  one-sided  attack  of  the  problem  of  ontogeny,  and  urged 
them  to  pay  attention  to  the  important  post-embryonic  stages,  down  to 
our  own  time,  students  of  recent  animals  have  for  the  most  part  been 
content  to  follow  the  beaten  path.  They  have  left  to  the  paleozoologist 
the  study  of  the  later  stages  in  the  life  history  of  the  individual,  and 
the  latter's  endeavors  in  this  direction  have  developed  the  science  of 
zoontogeny  as  to-day  understood.  There"  was,  perhaps,  a  natural  cause 
for  this  separation,  in  the  fact  that  the  student  of  soft  tissues  finds  few 
changes  which  he  deems  worthy  of  attention,  between  the  embryo  and 
the  adult;  whereas  the  student  of  hard  structures  generally  sees  an 
abundance  of  such  changes.  This  is  especially  true  of  invertebrates, 
more  particularly  of  such  as  build  external  hard  structures  in  which 
successive  additions  are  marked  by  the  lines  of  growth.  Vertebrates, 
and  invertebrates  without  permanent  hard  parts,  such  as  the  Crustacea, 
require  series  of  individuals  showing  the  successive  steps  in  develop- 
ment. But  mollusks,  brachiopods  and  corals  show,  by  their  incremental 
lines,  the  steps  in  the  life  history  during  the  post-embryonic  period,  so 
that  one  perfect  individual  suffices  to  present  these  later  stages  in 
development. 

It  is  not  infrequently  urged  that  the  hard  parts  of  invertebrates, 
especially  the  shells  of  mollusks,  are  not  reliable  indices  of  ontogenetic 
development,  since  they  represent  only  the  integument,  which  is  subject 
to  ready  modification  under  the  influence  of  the  environment.  Such  an 
argument  is  based  on  a  total  ignorance  of  the  relation  of  the  shell  or 
other  hard  structure  to  the  soft  parts  of  the  animal.  The  paleontolo- 
gist is  convinced  that  the  hard  parts  of  animals  are  the  best  indices  of 
its  development,  since  they  record  in  a  permanent  form  all  the  minute 
modifications  which  are  not  even  recognizable  in  the  soft  parts.  More 
than  this,  I  believe  that  shells,  those  of  mollusks  at  any  rate,  furnish 
us  with  a  record  of  changes  wholly  independent  of  the  environment,  and 
referable  entirely  to  an  inherited  impulse  towards  progressive  modifica- 
tion, along  definitely  determinable  lines.  I  am  well  aware  that  I  am 
not  expressing  the  opinion  of  all  paleontologists  in  this  statement,  and 
that  this  view,  moreover,  is  strongly  opposed  by  some  of  our  ablest 
European  conchologists.  But  here  again  I  contend  that  this  difference 


THE  PALEONTOLOGIC  RECORD  55 

of  opinion  is  due  to  a  difference  of  method.  When  the  student  of  shells 
directs  his  attention  chiefly  to  adult  characters,  this  definitely  directed 
variation,  independent  of  environment,  is  not  recognized  by  him.  But 
no  one  can  study  the  details  of  shell  ontogeny,  especially  in  the  earlier 
stages,  without  quickly  realizing  that  ontogenetic  development  is  ortho- 
genetic,  and  that  the  inherited  impulse  towards  determinate  modifica- 
tions is  the  most  powerful  controlling  factor  of  the  animal's  life  history. 

So  far  as  invertebrates  are  concerned,  the  study  of  post-embryonic 
development  was  first  seriously  undertaken  by  the  immortal  Hyatt,  in 
his  work  on  the  ammonites.  To  be  sure,  others  before  him — notably 
d'Orbigny — noticed  that  a  distinct  series  of  changes  was  recognizable  in 
the  shell  of  ammonites,  but  no  one  before  Hyatt  actually  employed  this 
method.  He  himself  once  told  me  that  when,  in  the  early  sixties,  he 
first  realized  the  importance  of  this  method  of  study  when  actually 
applied  to  shelled  organisms,  and  its  value  as  a  guide  in  phylogeny, 
it  seemed  so  marvelously  simple  that  he  felt  sure  that  the  method  and 
its  application  must  be  fully  understood  by  all  working  naturalists. 
"  But,"  he  added,  "  I  soon  found  that  I  practically  stood  alone,  and  I 
have  spent  my  life  since  in  the  endeavor  to  convert  them  to  my  point 
of  view/' 

This  misunderstanding,  on  the  part  of  many  zoologists,  of  the  onto- 
genetic method  has  given  rise  to  their  false  attitude  towards  the  doc- 
trine of  the  recapitulation  of  ancestral  characters.  This  subject  will 
be  adequately  treated  by  some  of  my  successors,  but  I  can  not  forbear 
to  anticipate  them  to  the  extent  of  pointing  out  this  fact:  When  the 
embryologist  seeks  for  proof  or  disproof  of  this  concept  in  the  enor- 
mously condensed  record  of  the  stages  between  the  ovum  and  birth,  he 
is  bound  to  be  grievously  disappointed;  for  this  record,  necessarily 
modified  by  eliminations,  can  only  furnish  general  resemblances  of  the 
embryo  to  earlier  types,  and  can  not  be  said  to  actually  recapitulate  the 
life  history  of  the  entire  race.  When,  however,  the  student  of  post- 
embryonic  ontogeny  compares  the  youthful  stages  of  an  individual  with 
the  adult  of  immediately  preceding  species  of  the  same  genetic  series, 
the  fact  of  recapitulation  becomes  at  once  apparent. 

The  post-embryonic  life  history  of  an  individual  falls  readily  into 
stages,  of  which  four  major  ones  have  been  recognized  and  named, 
chiefly  by  Hyatt.  These  are:  (1)  the  infant  or  nepionic  stage;  (2) 
the  adolescent  or  neanic  stage;  (3)  the  adult  or  ephebic  stage,  and 
(4)  the  senile  or  gerontic  stage,  followed  by  death.  These  onto-stages, 
as  they  may  be  called,  are  further  divided  into  substages,  designated  by 
the  prefixes  ana,  meta  and  para,  and  they  may  be  observed  in  the  ontog- 
eny of  all  individuals.  Moreover,  in  closely  related  members  of  one 
genetic  group,  the  duration  of  these  stages  and  substages  is  approxi- 
mately uniform.  Change  in  form,  however,  may  vary  greatly,  and  have 


5 6  ^THE  PALEONTOLOGIC  RECORD 

no  necessary  relation  to  the  onto-stages,  even  if  they  coincide  with  them. 
We  have  thus  a  second  group  of  stages,  which  we  may  designate  form 
stages,  or  morphic  stages,  and  there  will  be  required  distinct  designa- 
tions in  each  case.  The  best  method  of  naming  these  stages  is  to  refer 
them  to  the  adult  ancestral  type  which  they  represent. 

Thus,  in  all  species  of  the  gastropod  shell  Fusus,  the  earliest  morphic 
stages  are  a  close  recapitulation  of  the  adult  of  Fusus  porrectus  of  the 
Eocenic.  These  stages  may  therefore  be  called  the  F.  porrectus  stage. 
It  may  be  continued  for  a  considerable  period  of  the  early  life  history, 
covering  several  onto-stages,  or  it  may  be  condensed  into  a  short  por- 
tion of  one  stage  or  substage,  in  accelerated  individuals. 

It  is  of  considerable  importance  that  onto-stages  and  morphic  stages 
should  be  discriminated,  so  I  will  introduce  another  illustration. 

In  the  Miocenic  of  the  Atlantic  coast  we  have  the  gastropod  genus 
Fulgur  well  represented.  Fulgur  fusiformis  is  normally  characterized, 
in  the  adult,  by  the  possession  of  a  pronounced  flat  shoulder,  which  is 
separated  from  the  body  of  the  shell  by  an  angulation  carrying  rounded 
tubercles.  Some  of  the  more  specialized  individuals  lose  the  angula- 
tion and  tubercles  in  the  last  whorl  and  become  rounded.  Thus,  while 
normally  the  species  is  tuberculated  in  the  ephebic  onto-stages,  special- 
ized individuals  acquire  a  new  morphic  stage  through  the  loss  of  orna- 
mentation. This  morphic  stage  is  prophetic  of  the  normal  adult  of 
Fulgur  maximum,  and  hence  may  be  called  the  F.  maximum  stage. 
F.  maximum  itself  has  in  its  nepionic  onto-stage  the  characters  of 
adult  F.  fusiformis;  hence  it  may  be  designated  the  F.  fusiformis  stage. 
Some  individuals  acquire  a  new  stage,  namely,  a  spinous  stage,  char- 
acteristic of  the  adult  of  F.  carica.  In  the  type  designated  as  F. 
tritonis,  the  nepionic  stage  is  characterized  by  a  fusiformis  morphic 
stage,  the  neanic  largely  by  the  maximum  stage,  though  some  of  the 
later  neanic  stages  may  actually  acquire  the  carica  stage.  In  less 
specialized  individuals  the  maximum  stage  may  continue  into  the  early 
ephebic  in  more  specialized  ones  it  ceases  early  in  the  neanic,  the  carica 
stage  taking  its  place.  Finally,  Fulgur  carica  is  characterized  by  the 
elimination  of  the  maximum  morphic  stage,  so  that  the  neanic  as  well 
as  the  ephebic  onto-stages  are  characterized  by  the  spines  of  the  carica 
stage,  which  may  even  begin  in  the  late  nepionic. 

In  the  foregoing,  the  different  morphic  stages  are  shown  to  be 
telescoped  with  the  onto-stages,  appearing  either  earlier  and  earlier  in 
the  ontogeny  of  successive  individuals,  through  the  operation  of  the 
law  of  acceleration  or  tachygenesis ;  or  later  and  later,  through  the 
operation  of  the  complementary  law  of  retardation  or  bradygenesis. 
These  laws  are,  of  course,  only  applicable  to  an  orthogenetic  series,  but 
in  such  a  series  they  are  competent  to  produce,  by  interaction,  all 
conceivable  combinations  of  characters. 


THE  PALEONTOLOGIC  RECORD  57 

The  paleontologist,  more  than  any  other  naturalist,  is  concerned 
with  the  product  of  these  interactions,  and  to  him,  oftener  than  to 
others,  has  come  the  question,  Are  these  results  species  ?  and,  if  so,  what 
are  the  criteria  for  the  separation  of  species?  The  student  of  hard 
structures  appreciates  the  difficulty  of  drawing  sharp  lines,  and  one  of 
his  most  trying  tasks  is  to  satisfy  the  idiosyncrasies  of  his  colleagues  in 
the  making  of  species,  subspecies,  varieties,  etc.  The  student  of  hard 
parts  finds  transitional  forms  the  rule,  and  he  dare  not  grind  them  to 
powder  under  his  heel  with  the  remark  credited  to  Stimpson,  that 
"  that  is  the  proper  way  to  dispose  of  those  damned  transitional  forms." 

The  philosophic  paleontologist  recognizes  more  readily  than  any  one 
else  the  truth  of  the  dictum  that  nature  knows  only  individuals,  and 
that  species  are  special  creations,  called  into  being  by  the  fiat  of  the 
naturalist.  He  is  concerned  not  so  much  with  the  origin  of  species  as 
with  the  origin  of  individuals;  and  while  he  makes  use  of  the  artificial 
divisions  called  species,  and  sometimes  finds  his  chief  joy  in  multiplying 
and  subdividing  them,  he  still  recognizes  their  non-existence,  and  turns 
to  individuals.  He  may,  perhaps,  prefer  to  speak  of  mutations,  mean- 
ing individuals,  nevertheless. 

But  individuals  are  complex  entities,  and  the  paleontologist  can  not 
investigate  their  genesis  before  he  has  thoroughly  investigated  the  origin 
of  the  parts  composing  it.  As  Professor  Osborn  has  said,  the  paleo- 
zoologist  is  concerned  primarily  with  the  origin  of  structures.  He 
alone  is  able  to  trace  their  development,  for  he  is  present  at  their  birth, 
he  follows  their  whole  history,  and  will  be  present  also  at  their  extinc- 
tion, for  the  paleontologist  alone  is  immortal. 

PALEONTOLOGY    AND    THE    EECAPITULATION    THEORY 

BY  E.  R.  CUMINGS 

INDIANA  UNIVERSITY 

I 

BATHER  once  said  that  "  If  the  embryologists  had  not  forestalled 
them,  the  paleontologists  would  have  had  to  invent  the  theory 
of  recapitulation."  This  may  be  considered  as  a  fair  sample  of  the 
attitude  of  at  least  the  Hyatt  school  of  paleontologists  toward  the  theory. 
It  is  doubtful  if  any  paleontologist  could  be  found  who  wholly  rejects  it. 

In  violent  contrast  with  the  more  or  less  complete  acceptance  of 
the  theory  by  paleontologists,  is  the  attitude  of  many  embryologists 
and  zoologists.  Montgomery  and  Hurst  have  perhaps  put  the  case 
against  recapitulation  more  strongly  than  any  one  else.  The  former 
says,  for  example, 

The  method  is  wrong  in  principle,  to  compare  an  adult  stage  of  one  organism 
with  an  immature  stage  of  another. 


58  THE  PALEONTOLOGIC  RECORD 

And  again: 

Therefore  we  can  only  conclude  that  the  embryogeny  does  not  furnish  any 
recapitulation  of  the  phylogeny,  not  even  a  recapitulation  marred  at  occasional 
points  by  secondary  changes. 

Hurst  is  even  more  emphatic.     He  says: 

The  ontogeny  is  not  an  epitome  of  the  phylogeny,  is  not  even  a  modified 
or  "  falsified "  epitome,  is  not  a  record,  either  perfect  or  imperfect  of  past 
history,  is  not  a  recapitulation  of  evolution. 

It  would  seem  as  though  two  statements  could  scarcely  be  more 
flatly  contradictory  than  those  of  Bather  and  Hurst,  just  quoted. 
Nevertheless,  I  venture  to  make  the  assertion  that  both  parties  to  the 
recapitulation  controversy  are  right,  for  the  simple  reason  that  they  are 
not  talking  about  the  same  thing.  Grabau  has  called  attention  to  this, 
by  implication,  in  one  of  his  papers  on  gastropods.  He  states  that  the 
recapitulation  theory  has  been  placed  in  an  evil  light  by  the  habit  of 
embryologists  of  comparing  embryonic  stages  with  the  adults  of  exist- 
ing representatives  of  primitive  types,  and  that  they  have  commonly 
neglected  to  compare  the  epembryonic  stages  with  the  adults  of  geolog- 
ically older  species.  In  other  words,  paleontologists  have  usually  dealt, 
in  their  comparisons,  with  epembryonic  stages,  and  embryologists  with 
embryonic  stages. 

There  arises  here  a  question  of  definition:  does  the  biogenetic  law 
mean  that  the  ontogeny  is  a  recapitulation  of  the  phylogeny,  or  does 
it  mean  that  the  embryogeny  is  a  recapitulation  of  the  phylogeny? 
If  we  take  the  general  consensus  of  opinion,  we  shall  find  for  the  former 
definition;  and  if  we  take  the  words  of  Haeckel,  whose  statement  of 
the  law  is  the  one  usually  quoted,  we  shall  again  find  for  the  former 
definition. 

It  is  certainly  true,  at  any  rate,  that  the  epembryonic  stages  may 
and  do  show  recapitulation,  even  when  the  embryonic  stages  do  not,  or 
when  the  embryogeny  is  so  obscured  by  secondary  adaptations  as  to  be 
untrustworthy.  There  are  many  reasons  why  adaptations  should  occur 
in  intra-uterine  or  larval  life  to  obscure  the  ancestral  record.  These 
have  often  been  stated  and  discussed,  and  I  shall  pass  them  with  this 
mere  mention.  That  the  record  of  remote  ancestors,  contained  in  the 
embryogeny,  may  be  lost  or  obscured,  while  the  record  of  nearer  ances- 
tors, contained  in  the  epembryogeny,  is  still  clear  and  convincing,  is 
my  contention;  and  I  hold  that  this  contention  is  substantiated  by  the 
studies  of  a  host  of  paleobiologists. 

While  contrasting  the  views  of  biologists  and  paleobiologists,  I  do 
not  wish  to  create  the  impression  that  all  of  the  former  have  turned 
against  the  theory  of  recapitulation.  Several  recent  studies  of  the 
development  of  extant  forms  seem  to  afford  very  satisfactory  evidence 
that  the  theory  is  not  wholly  rejected  in  the  house  of  its  fathers.  Of 


THE  PALEONTOLOGIC  RECORD  59 

these  I  may  mention  the  very  interesting  papers  by  Griggs  on  juvenile 
kelps,  Zeleny  on  the  development  and  regeneration  of  serpulids,  and 
Eigenmann  on  the  blind  vertebrates  of  North  America. 

Griggs  especially  criticizes  the  views  of  such  critics  of  recapitula- 
tion as  His,  who  holds  that  the  reason  why  ontogeny  seems  to  recapitu- 
late pbylogeny  is  because  the  developing  organism  must  from  physiolog- 
ical necessity  pass  from  less  to  more  complex  stages,  more  or  less 
resembling  ancestral  forms;  and  the  views  of  Morgan,  who  holds  that 
only  embryonic  stages  of  ancestors  are  repeated.  This  is  the  so-called 
"  Repetition  Theory."  To  both  of  these  critics  Griggs  objects  that 
they  confuse  physiology  and  morphology.  "  The  recapitulation  the- 
ory," he  says,  "  has  nothing  to  do  with  physiology ;  it  is  purely  a  matter 
of  morphology." 

On  the  first  point,  that  the  developmental  stages  are  merely  the 
physiologically  necessary  steps  in  the  development  of  the  adult  organ- 
ism, the  conclusions  of  Eigenmann  and  Zeleny  are  of  especial  interest. 
Eigenmann  shows  that  in  the  blind  fish,  Amblyopsis,  the  development 
of  the  foundations  of  the  eye  is  normal,  and  is  phylogenic,  while  the 
stages  beyond  the  foundations  are  direct.  Zeleny  concludes  that  the 
ontogenesis  of  the  opercula  of  serpulids  is  phylogenic,  and  recapitulates 
ancestral  characters;  but  the  regeneratory  development  of  the  organ  is 
direct,  and  may  be  very  different  from  the  ontogenetic  development. 
We  may  ask,  therefore,  if  development  takes  a  certain  course  only  be- 
cause that  is  the  physiologically  necessary  way  in  which  the  individual 
or  the  organ  must  develop,  why  should  a  condition  of  perfect  blindness, 
with  almost  total  loss  of  all  the  eye  structures,  be  attained  only  by  the 
round-about  method  of  first  developing  the  foundations  of  a  normal 
eye?  Why,  again,  if  there  is  any  physiologically  necessary  course  of 
development,  should  the  serpulid  be  able  to  regenerate  the  opercula  in 
a  manner  entirely  different  from  their  ontogenesis  ? 

Hatschek,  Hurst,  Montgomery  and  others  maintain  that,  if  two 
individuals  differ  in  the  adult,  they  must  also  differ  in  the  egg,  and 
consequently  must  be  different  at  all  stages  between.  From  this  thesis 
they  draw  the  conclusion  that  organisms  can  not  recapitulate  adult 
ancestral  characters,  because  any  change  in  the  adult  stage  of  an  indi- 
vidual, causing  it  to  be  different  from  its  parents,  involves  a  change  in 
the  entire  ontogeny — "  the  entire  row  of  cells  "  from  the  egg  to  the 
adult.  That  there  is  some  sort  of  change  in  the  entire  row  of  cells  we 
grant;  but  that  this  change  necessarily  affects  the  morphology  of  the 
individual  or  of  its  organs,  up  to  the  adult  stage,  we  do  not  grant. 
We  have  here  again  a  confusion  of  morphology  and  physiology.  The 
cell  energies  may  indeed  be  changed ;  but  unless  a  change  in  the  cell 
energies  inevitably  necessitates  a  change  in  the  morphology  of  all  the 
cells  or  of  all  the  organs  which  they  compose,  the  argument  of  Mont- 
gomery proves  nothing. 


60  THE  PALEONTOLOGIC  RECORD 

If  inheritance  were  perfect,  the  individual  would  take  exactly  the 
same  course  in  development  as  its  ancestors.  That  it  does  not  do  this 
in  all  cases  is  a  more  remarkable  fact  than  that  in  so  many  cases  it 
follows  the  ancestral  mode  of  development  so  closely.  This  loss  of 
inheritance  is  due  to  a  progressive  condensation  of  ontogeny,  or  as  it  is 
commonly  called,  acceleration.  Most  embryologists  misconceive  the  law 
of  acceleration,  limiting  it  to  the  omission  of  characters  or  stages. 
With  the  classic  formulation  of  the  law  by  Hyatt  we  are  all  familiar. 
According  to  Hyatt,  acceleration  involves  not  only  omission,  but  con- 
densation without  omission,  through  the  earlier  inheritance  of  char- 
acters acquired  in  the  adult  or  adolescent  stages  of  life.  By  the  un- 
equal acceleration  of  characters  an  overlapping,  or  telescoping,  as 
Grabau  calls  it,  may  be  introduced.  It  follows,  therefore,  that  accel- 
eration may  be  by  elimination,  by  condensation  without  change  in  the 
order  of  appearance  of  characters,  and  by  condensation  with  change  in 
the  order  of  appearance,  or  telescoping.  As  conceived  by  the  paleo- 
biologist,  the  law  of  acceleration  is  an  explanation  of  recapitulation,  as 
well  as  an  explanation  of  the  failure  to  recapitulate. 

Another  factor  in  inheritance  is  retardation,  so  named  by  Cope. 
By  the  operation  of  this  law,  characters  that  appear  late  in  the  ontogeny 
may  disappear  in  the  descendents,  because  development  terminates 
before  the  given  characters  are  reached.  In  this  way  the  ontogeny 
may  be  shortened  and  simplified,  and  many  ancestral  characters  may  be 
lost  entirely.  The  result  of  the  continued  operation  of  retardation  is 
retrogression,  since  the  loss  of  the  characters  of  nearer  ancestors,  with 
the  continued  repetition  in  early  ontogeny  of  the  characters  of  remote 
ancestors,  must  eventually  cause  the  species  to  resemble  the  remote, 
rather  than  the  nearer,  ancestors. 

II 

Of  the  numerous  cases  adduced  by  paleontologists,  in  which  there 
is  clear  evidence  of  recapitulation,  I  shall  mention  a  few  only. 

Probably  the  best  known  examples  of  recapitulation  are  those  made 
known  by  the  researches  of  Hyatt,  Branco,  Wiirtenburger,  Buckman, 
Smith  and  others  among  the  Cephalopoda.  It  is  shown  that  Ammon- 
ites pass  through  a  goniatite  stage,  and  that,  as  phrased  by  Zitttel, 
"  The  inner  whorls  of  an  ammonite  constantly  resemble  in  form,  orna- 
ment and  suture  line  the  adult  condition  of  some  previously  existing 
genus  or  other."  The  nautilus  grows  at  first  straight  or  orthocera- 
form,  then  arched  or  cyrtoceraform,  and  finally  at  the  close  of  the  first 
volution  of  the  shell,  becomes  close  coiled.  The  impressed  zone  appears 
in  ancient  nautiloidea  in  the  neanic  stage,  where  the  whorls  first  come 
into  contact,  and  is  indeed  a  result  of  contact.  In  modern  nautilus, 
and  in  Mesozoic  and  Tertiary  nautilus  the  impressed  zone  appears  in 


THE  PALEONTOLOGIC  RECORD  61 

the  nepionic  stage,  before  the  whorls  come  into  contact.  It  has  been 
carried  back  in  the  ontogeny  by  acceleration.  Smith  concludes  from  a 
study  of  the  development  and  phylogeny  of  Placenticeras,  an  Upper 
Cretaceous  ammonoid,  that  "the  development  of  Placenticeras  shows 
that  it  is  possible,  in  spite  of  dogmatic  assertions  to  the  contrary,  to 
decipher  the  race  history  of  an  animal  in  its  individual  ontogeny." 

'Among  the  Gastropoda,  Grabau  and  Burnett  Smith  have  pointed 
out  numerous  beautiful  cases  of  recapitulation.  In  Fusus  and  its  allies, 
the  higher  forms  quite  constantly  resemble  in  their  earlier  stages  the 
adults  of  ancestral  forms.  Even  in  profoundly  modified  gerontic  types, 
the  young  resemble  the  ancestors.  Smith  has  brought  to  light  in 
Athleta  (Volutilithes)  of  the  Eocene,  an  almost  perfect  example  of  even 
and  regular  acceleration,  with  its  correlative,  the  recapitulation  in  the 
young  of  the  Upper  Eocene  forms  of  the  adult  characters  of  the  Lower 
Eocene  forms.  The  stages  passed  through  by  this  group  of  shells  are, 
beginning  with  the  earliest,  a  smooth,  curved  rib,  cancellated,  spiny 
and  sometimes  a  senile  stage.  In  the  ancestral  species  (A.  limopsis) 
the  curved  rib  stage  comes  in  at  the  close  of  the  fourth  whorl,  whereas 
in  the  Upper  Eocene  form  (A.  petrosa),  this  stage  comes  in  at  the 
beginning  of  the  third  whorl. 

Among  the  Pelecypoda  the  classic  researches  of  Jackson  are  familiar 
to  all.  He  shows  that  the  modern  Pecten  passes  through,  in  its  on- 
togeny, a  series  of  stages  resembling  adult  Rhombopteria,  Pterinopecten 
and  Aviculopecten,  and  that  the  geologic  order  of  these  genera  is  the 
same  as  the  ontogenetic  order  in  Pecten.  In  such  monomyarian  genera 
as  Ostrea,  the  initial  shell,  or  prodissoconch,  is  dimyarian,  and  resembles 
the  primitive  Nucula.  Again,  in  various  more  or  less  widely  separated 
genera,  the  condition  of  complete  cemented  fixation  has  produced  the 
ostreaform  shape.  Each  one  of  these  genera,  however,  except  where 
the  modification  of  shape  due  to  fixation  appears  very  early  in  ontogeny, 
recapitulates  the  adult  characters  of  its  respective  ancestor.  The  ex- 
amples of  this  are  Mulleria,  a  member  of  the  Unionidae — like  Anodon 
in  the  young;  Hinnites,  a  member  of  the  Pectinacea — like  Pecten  in 
the  young;  Spondylus,  another  member  of  the  Pectinacea — like  Pecten 
in  the  young. 

Beecher's  various  studies  of  the  Brachiopoda  not  only  brought  out 
the  fact  that  the  initial  shell  or  protegulum  of  the  brachiopod  is  remark- 
ably similar  to  the  most  primitive  known  Lower  Cambrian  brachiopods, 
but  have  supplied  in  addition  numerous  other  remarkable  examples  of 
recapitulation.  One  of  the  most  striking  of  these  is  the  case  of  the 
Terebratellidae.  In  both  the  boreal  and  austral  subfamilies  a  very  com- 
plete series  of  genera  correspond  to  the  ontogenetic  stages  of  the  ter- 
minal or  highest  genera.  Another  interesting  case  is  that  of  Orbicu- 
loidea.  This  discoid  shell  has  at  first  a  straight  hinge  like  Iphidea. 


62  THE  PALEONTOLOGIC  RECORD 

It  next  resembles  Obolella,  then  at  a  later  stage  it  is  like  Schizo  crania, 
and  finally  adult  growth  brings  in  the  characters  of  Orbiculoidea. 
Raymond  has  shown  the  remarkable  similarity  of  the  neanic  stage  of 
Spirifer  mucronatus  to  the  adult  8.  crispus  of  the  Niagara.  Shinier 
and  Grabau  found  in  the  upper  Hamilton  of  Thedford,  Ontario,  a 
variety  of  Spirifer  mucronatus  that  is  very  mucronate  in  the  young 
and  not  at  all  so  in  the  adult.  The  derivation  of  this  form  from 
8.  mucronatus  is  beyond  question.  I  have  pointed  out  a  precisely 
similar  case  in  Platystrophia  acutilirata  var.  senex.  This  variety, 
which  occurs  in  the  upper  Whitewater  beds  of  Indiana  and  Ohio,  has 
a  hinge  angle  of  nearly  90°  in  the  adult.  In  the  young,  however,  the 
outlines  of  the  shell  are  exactly  like  the  typical  P.  acutilirata,  from 
which  it  is  beyond  any  question  descended.  Greene  has  shown  that 
Clionetes  granulifer  of  the  Carboniferous  is,  in  the  neanic  stage,  like 
the  Devonian  Chonetes,  and  that  the  hinge-spines  come  in  at  a  consid- 
erably earlier  stage  in  the  Carboniferous  than  in  the  Devonian  and 
Silurian  forms,  showing  the  acceleration  of  this  character. 

In  the  Bryozoa  I  have  pointed  out  the  fact  that  the  colony  behaves 
as  an  individual,  and  like  an  individual  recapitulates  in  its  ontogeny 
(astogeny)  ancestral  characters.  This  is  beautifully  shown  in  Fenes- 
tella,  in  which  the  earlier  zocecia  are  strikingly  like  the  adult  zocecia  of 
the  Cyclostomata.  The  adolescent  zooecia  of  Devonian  Fenestella  are 
similar  to  the  adult  zooecia  of  Niagara  forms.  Lang  has  brought 
together  numerous  cases  of  recapitulation  among  Jurassic  and  Creta- 
ceous Stomatopora  and  Proloscina.  The  method  of  dichotomy  in  the 
earlier  portions  of  the  colony  is  constantly  more  like  the  normal  dichot- 
omy of  ancestral  species. 

In  graptolites  the  remarkable  researches  of  Ruedemann  clearly 
indicate  that  the  graptolite  colony  recapitulates  ancestral  characters, 
the  proximal  thecae  being  similar  to  ancestral  adult  thecae.  He  says: 

The  rhabdosomes  in  toto  and  their  parts,  the  branches,  seem  also  to  pass 
through  stages  which  suggest  phylogenetically  preceding  forms. 

Among  the  trilobites  the  studies  of  Beecher,  Walcott  and  Matthew 
are  classic.  Beecher  has  shown  that  there  is  a  common  larval  form, 
the  protaspis,  and  that  in  higher  genera  characters  appear  in  the  pro- 
taspis  that  are  known  only  in  the  adults  of  more  primitive  genera. 
For  example,  the  "  main  features  of  the  cephalon  in  the  simple  protaspis 
forms  of  Solenopleura,  Liostracus  and  Ptychoparia  are  retained  to 
maturity  in  such  genera  as  Carausia  and  Acontheus"  Larval  Sao  has 
characters  that  occur  in  the  adult  of  Ctenocephalus.  The  larval  stages 
of  Dalmanites  and  Proetus  have  characters  that  appear  only  in  the  adult 
of  ancient  genera. 

Among  the  corals  Beecher  and  Girty  show  that  such  genera  as 
Favosites  have  early  stages  that  suggest  Aulopora.  Lang,  in  a  recent 


THE  PALEONTOLOGIC  RECORD  63 

paper,  records  very  interesting  cases  of  recapitulation  in  the  genus 
Parasmilia  of  the  Cretaceous.  -  Bernard  concludes  that  the  coral  colony, 
like  the  graptolite  colony  and  the  bryozoan  colony,  behaves  as  an 
individual. 

In  the  echinoderms  the  likeness  of  the  stem  ossicles  and  the  devel- 
opment of  the  anal  plate  of  Antedon,  to  Paleozoic  and  Mesozoic  forms 
has  become  one  of  the  stock  illustrations  of  recapitulation.  Jackson 
has  found  interesting  examples  of  recapitulation  in  the  development  of 
the  ambulacral  and  inter-ambulacral  plates  of  echinoids.  Miss  Smith 
has  shown  that  the  young  Pentremites  is  exactly  similar  in  form  to  the 
adult  Cadaster.  This  is  an  extremely  interesting  case,  for  Bather  has 
independently,  and  from  quite  different  data,  come  to  the  conclusion 
that  Pentremites  is  derived  from  Cadaster. 

The  idea  of  recapitulation  has  been  one  of  the  most  fertile  in  the 
whole  realm  of  biology,  and  its  usefulness  to  the  paleobiologist  has  been 
almost  incalculable.  But  while  there  can  be  no  doubt  that  recapitula- 
tion is  a  fact,  the  paleontologist  should  observe  all  due  care  not  to 
assume  too  much  for  it.  That  there  are  various  sorts  of  adaptations, 
arising  at  all  stages  of  life,  and  that  these  may  greatly  obscure  the 
ancestral  record,  is  a  fact  too  well  known  to  require  more  than  mention. 
There  is  also  always  acceleration,  sometimes  affecting  different  char- 
acters very  unequally ;  and  there  may  be  retardation.  All  of  these  fac- 
tors complicate  the  record  of  ontogeny.  Nevertheless,  after  all  of  these 
have  been  taken  duly  into  consideration,  the  parallel  between  ontogeny 
and  phylogeny  remains  a  powerful  aid  to  investigation  for  the  pale- 
ontologist. 

VERTEBRATE  PALEONTOLOGY  AND  THE  EVIDENCES 
FOR  RECAPITULATION 

BY  L.  HUSSAKOF 

AMERICAN   MUSEUM  OF   NATURAL  HISTORY 

AFTER  the  careful  papers  of  Professors  Loomis  and  Lull  in  which 
the  doctrine  of  recapitulation  was  so  fully  set  forth  from  the 
standpoint  of  vertebrate  paleontology,  I  can  perhaps  do  no  better  than 
devote  part  of  the  time  allotted  me  to  showing  how  certain  leading 
vertebrate  paleontologists  have  viewed  this  question.  Then  I  will  cite 
one  or  two  illustrations  of  this  principle  drawn  from  among  the  lower 
vertebrates. 

Passing  over  the  period  of  pre-Darwinian  paleontology — the  pale- 
ontology of  Cuvier,  Owen  and  Louis  Agassiz — we  come  to  the  time  of 
Leidy,  who,  as  Professor  Osborn  has  recently  shown,1  was  one  of  the  first, 

1  In  his  address  on  "  Darwin  and  Paleontology "  printed  in  "  Fifty  Years 
of  Darwinism."  Centennial  addresses  in  honor  of  Charles  Darwin,  New  York, 
1909,  p.  209. 


64  THE  PALEONTOLOGIC  RECORD 

if  not  the  first,  to  bring  the  fruits  of  paleontology  to  the  support  of 
evolution.  But  Leidy,  as  far  as  a  hasty  search  through  his  writings 
could  reveal,  nowhere  expressly  advocated  the  doctrine  of  recapitula- 
tion. Indeed,  he  gave  but  little  attention  to  the  philosophical  bearings 
of  paleontology,  generally  partly  because  of  temperament  and  partly 
because  in  those  pioneer  days  material  to  serve  as  a  basis  for  generaliza- 
tion was  still  scanty. 

Gaudry,  one  of  the  first  European  paleontologists  to  champion  the 
cause  of  evolution,2  likewise  did  not  specially  advocate  the  doctrine 
of  recapitulation.  An  examination  of  his  "  Philosophic  Paleontolo- 
gique  "  fails  to  reveal  any  definite  belief  in  this  doctrine. 

Huxley,  as  far  as  I  can  gather  from  his  papers  and  essays,  be- 
lieved in  this  doctrine,  though  with  certain  implied  reservations  as  to  its 
general  applicability.  In  his  presidential  address  to  the  Geological 
Society  of  London  on  "  Paleontology  and  the  Doctrine  of  Evolution  " 
delivered  in  1870,  we  find  some  interesting  comment  on  the  signifi- 
cance of  the  splints  of  the  living  horse,  which  he  regards  as  indicative 
of  the  presence  of  three  complete  digits  in  the  horse  ancestor.  But 
Huxley  was  never  an  out-and-out  advocate  of  the  biogenetic  law. 

Cope  and  Marsh,  as  we  all  know,  were  staunch  upholders  of  evolu- 
tion ;  and  Cope,  at  least,  was  also  a  staunch  upholder  of  the  doctrine  of 
recapitulation.  In  his  "  Primary  Factors  of  Organic  Evolution,"  his 
last  contribution  to  philosophical  paleontology,  he  devotes  considerable 
space  to  proving  this  doctrine.  He  says  :3 

The  representatives  of  each  class  passed  through  the  stages  which  are 
permanent  in  the  classes  below  them  in  the  series. 

And  he  backs  up  this  proposition  with  evidence  derived  from  the 
ontogeny  and  phylogeny  of  batrachia,  the  antlers  of  deer  and  the  blood 
trunks  of  vertebrates  generally.  For  all  that,  Cope  recognized  the 
justice  of  certain  criticisms  which  had  been  brought  against  the  doc- 
trine of  recapitulation  and  urged  caution  in  its  application. 

An  example  or  two  of  recapitulation  may  now  be  cited  from  the 
field  of  the  lower  vertebrates. 

The  mode  of  development  of  the  teeth  in  Neoceratodus  has  some- 
times been  adduced  as  an  illustration  of  recapitulation.  It  is  well 
known  that  the  Devonic  dipnoans  (e.  g.,  Dipterus)  had  teeth  com- 
posed of  rows  of  denticles,  those  in  each  row  being  more  or  less  fused 
at  their  bases.  During  the  history  of  the  dipnoans  since  the  Devonic 
period,  the  separate  denticles  have  merged  more  and  more  until  in 
Ceratodus  and  the  living  Neoceratodus,  the  rows  of  denticles  are,  in 

2  According  to  a  letter  from  Darwin  to  Gaudry  dated  Jamury  21,  1868. 
"The  Life  and  Letters  of  Charles  Darwin,"  edited  by  his  son  Francis  Darwin, 
New  York,  1899,  Vol.  II.,  p.  269. 

8 "  Primary  -Factors  of  Organic  Evolution,"  Chicago,  1896,  p.  195. 


THE  PALEONTOLOGIC  RECORD  65 

the  adult,  replaced  by  almost  smooth  ridges.  Now,  Semon  in  his 
beautiful  studies  on  the  development  of  Neoceratodus*  has  shown  that 
the  teeth  of  this  fish  at  one  stage  in  ontogeny,  are  represented  by  rows 
of  denticles  even  more  discrete  than  the  denticles  in  the  Devonic  Dip- 
terus;  then  the  denticles  gradually  merge  at  their  bases,  the  separate 
cusps,  however,  still  showing — a  stage  comparable  with  the  Carbonifer- 
ous Ctenodus;  then  they  merge  still  more  and  assume  the  ridge-like 
form  seen  in  the  adult  Neoceratodus. 

Another  example:  In  many  sharks  the  alimentary  canal  is 
longer  in  the  embryo  than  in  the  adult,  the  anal  opening  being  situ- 
ated near  the  posterior  end  of  the  trunk.  From  such  cases  one  is  in- 
clined to  believe  that  in  the  ancestral  sharks  this  must  have  been  the 
condition  in  the  adult  form;  that  is  to  say,  the  anal  opening  probably 
was  near  the  posterior  termination  of  the  trunk.  We  may  therefore 
ask:  are  there  any  early  fossil  sharks  which  show  such  a  condition? 
Eecently  Professor  Dean  has  described5  a  remarkable  specimen  of 
Cladoselache  from  the  Upper  Devonic  of  Ohio  which  seems  to  indicate 
such  a  condition.  In  this  specimen  remnants  of  both  kidneys  are  pre- 
served. They  extend  in  the  posterior  half  of  the  fish  and  by  their  direc- 
tion indicate  that  they  were  drawn  together,  toward  their  external 
opening,  not  far  from  the  posterior  termination  of  the  trunk.  This 
shows  that  the  anal  opening  in  this  ancestral  shark  was  very  much  as  in 
the  early  shark  embryo  to-day. 

In  conclusion  perhaps  I  may  venture  to  make  one  other  point 
in  regard  to  this  question.  A  vast  amount  of  skepticism  concern- 
ing the  doctrine  of  recapitulation  is  to  be  found  in  the  literature 
of  to-day;  and  if  we  study  the  reasons  for  this  skepticism  we  find 
that  it  is  in  some  measure  justified.  It  is  clearly  established  that  among 
vertebrates  as  well  as  among  invertebrates  there  are  many  examples  of 
structures  appearing  during  embryonic  growth  which  are  identical 
with  structures  found  in  the  adult  of  some  remote  ancestor.  But 
when  we  reflect  on  the  amount  of  adaptation  which  any  embryo 
has  undergone  in  its  long  evolutional  history;  when  we  remember 
how  palingenetic  characters  are  on  every  hand  overlaid  by  ceno- 
genetic  ones;  who  will  say  that  recapitulation  is  a  principle  of  gen- 
eral application,  or  that  it  is  safe  to  draw  conclusions  from  all  em- 
bryos concerning  their  long  extinct  ancestors?  Who  will  believe  that 
a  bony  fish  which  runs  through  its  embryonic  development  in  a  few 
days  repeats  its  ancestral  history,  when  we  see  at  every 'stage  of  its 
ontogeny  how  it  has  been  adaptively  modified  for  this  and  for  that 
special  need?  Only  when  series  of  related  forms  have  certain  onto- 

4  "  Die  Zahnentwickelung  des  Ceratodm  forsteri,"  "  Zool.  Forsch.  in  Austral, 
u.  Malay.  Archipel.,"  1899,  pp.  115-135,  pis.  xviii-xx. 

5  Mem.  Amer.  Hus.  Nat.  Hist.,  Vol.  IX.,  p.  232. 


66  THE  PALEONTOLOGIC  RECORD 

genetic  stages  in  common  are  we  justified  in  inferring  that  their 
racial  ancestor  may  have  had  such  characters  in  the  adult  state.  But 
it  should  never  be  lost  sight  of  that  this  inference  is  only  a  provi- 
sional hypothesis  which  may  or  may  not  be  verified  when  the  paleonto- 
logic  record  is  more  complete.  It  is  no  surprise  that  the  efforts  of 
some  earnest  paleontologists  have  been  discredited  in  some  quarters, 
especially  among  zoologists.  Some  of  them  have  invoked  recapitula- 
tion as  a  sort  of  magic  spell  by  which  they  can  conjure  up  ancestral 
forms  from  almost  any  embryonic  series,  forgetting  the  limitations  of 
this  doctrine.  As  far  as  the  attitude  of  vertebrate  paleontologists  is 
concerned,  their  view  has  been  aptly  summarized  by  Professor  Charles 
Deperet  in  his  book  "  Les  Transformations  du  Monde  Animal "  and  I 
can  do  no  better  than  close  with  a  quotation  from  him : 

If  we  appeal  to  paleontology,  it  must  be  recognized  that  this  hypothesis 
[recapitulation]  is  by  no  means  verified.  There  do  exist  here  and  there  certain 
fossil  genera,  which  all  their  lives  have  retained  certain  youthful  characteristics 
apparent  in  their  living  descendants ;  but  when  it  comes  to  reconstructing  whole 
series  chronologically  continuous,  grave  contradictions  are  met  with,  and  it  is 
only  in  the  groups  of  the  mammals  and  perhaps  of  the  reptiles  [and,  we  may 
add,  fishesl  that  it  becomes  possible  to  present  a  few  examples  sufficiently 
demonstrative.6 

6 "Les  Transformations  du  Monde  Animal,"  Paris,  1907,  p.  117. 


THE  PALEONTOLOGIC  RECORD  67 


THE  KELATION  OP  PALEOBOTANY  TO  PHYLOGENY 

BY  PBOFESSOR  D.  P.  PENHALLOW 

MCGILL   UNIVERSITY 

THE  history  of  plant  life  has  been  the  central  idea  in  all  botanical 
studies  from  the  very  earliest  times,  whether  expressed  in  the 
imperfect  methods  of  the  early  German  and  Dutch  botanists  who  de- 
sired simply  to  establish  natural  affinities  on  the  basis  of  external  re- 
semblances, or  in  the  ambitions  of  Csesalpino  to  arrive  at  a  classifica- 
tion of  plants  which  should  satisfy  the  conditions  of  relationship 
through  the  structure  of  all  parts,  and  especially  of  the  reproductive 
organs.  For  nearly  four  hundred  years  the  external  organs  have  been 
employed  as  the  chief  basis  of  those  numerous  systems  of  classification 
which  have  appeared  from  time  to  time.  The  idea  that  the  reproduc- 
tive organs  and  the  minute  interior  structure  of  plants  were  of  primary 
importance  as  first  advocated  by  Caesalpino,  was  for  a  long  time  lost  to 
view,  although  it  reappeared  now  and  then  in  the  works  of  later  writers. 
Eventually  it  gained  recognition  and  became  a  factor  of  increasing  im- 
portance, until  the  most  advanced  systems  now  employed  involve  an 
acceptance  of  both  the  external  parts  and  the  internal  anatomy  as  es- 
sential factors. 

From  the  time  of  Malpighi  and  Grew,  to  Goeppert  and  Corda,  our 
knowledge  of  the  interior  structure  of  plants  made  great  and  rapid 
progress,  and  was  later  applied  successfully  by  various  investigators  in 
the  direction  of  establishing  relationships.  To  no  one  are  we  more 
fully  indebted  for  an  elaboration  of  this  idea  than  to  Williamson,  whose 
researches  into  the  structure  of  fossil  plants  from  the  Coal  Measures 
of  Great  Britain,  during  the  latter  part  of  the  last  century,  laid  the 
real  foundation  of  modern  paleobotany. 

In  so  brief  a  treatment  as  that  which  is  now  employed,  it  is  impos- 
sible to  more  than  touch  upon  some  of  the  salient  features  in  the  rela- 
tions of  paleobotany  to  the  course  of  phylogeny,  but  it  is,  nevertheless, 
tforth  while  to  give  special  emphasis  to  the  now  well-recognized  fact 
that  a  thorough  knowledge  of  the  interior  structure  of  the  plant,  and 
especially  of  the  stem,  leads  to  a  more  comprehensive  and  exact  ac- 
quaintance with  relationships  than  that  of  any  other  part.  This  arises 
from  the  fact  that  the  minute  anatomical  details  have  a  greater  degree 
of  stability  than  any  other  portion  of  the  body,  doubtless  due  to  the  fact 
that  in  its  adjustment  to  the  land  habit,  the  environmental  influences 


68  THE  PALEONTOLOGIC  RECORD 

present  the  least  variable  features  in  those  factors  which  determine  re- 
lations to  mechanical  stress  and  physiological  needs. 

External  organs  are  notoriously  subject  to  variation,  even  under 
slight  alterations  of  surrounding  conditions,  within  the  limits  of  the 
species  or  even  within  various  stages  of  development  of  the  same  indi- 
vidual. From  this  it  is  clear  that  organs  such  as  leaves  must  be  very 
unreliable  for  phylogenetic  purposes.  It  is,  unfortunately,  true  that 
much  of  the  paleobotanical  work  based  upon  a  study  of  such  parts  must 
be  of  inferior  value,  and  the  conclusions  drawn  will  require  extensive 
revision  when  the  more  rigid  tests  to  be  applied  through  a  knowledge 
of  the  stem  structure  are  brought  to  bear. 

The  value  of  paleobotanical  evidence  consists  in  its  ultimate  corre- 
lation with  known  types  of  plants,  and  it  is  obvious  that  all  such  studies 
should  be  prosecuted  with  direct  reference  to  the  broader  require- 
ments of  plant  biology.  This  involves  a  comprehensive  knowledge  of 
the  history  of  plant  life  from  its  earliest  development;  that  the  data 
derived  from  a  study  of  living  species  should  be  correlated  with  the  evi- 
dence obtained  from  fossilized  remains.  Existing  vegetation  shows  a 
very  incomplete  record  of  plant  life  as  a  whole.  Its  history  as  known 
until  very  recent  times,  and  even  now  to  a  very  large  extent,  is  dis- 
played only  through  the  medium  of  detached  groups,  and  relates  chiefly 
to  the  most  highly  organized  types.  Through  the  perspective  afforded 
by  paleobotany,  it  becomes  possible  to  not  only  supply  missing  facts, 
but  to  establish  what  theory  has  for  so  long  a  time  required  a  satisfac- 
tory demonstration  of — a  more  or  less  continuous  series  of  phenomena 
from  the  rudimentary  forms  to  the  most  advanced  organisms. 

Until  a  very  recent  date  the  Linnsean  division  of  plant  life  into  two 
great  phyla,  the  cryptogams  and  the  phanerogams,  was  the  prevailing 
conception  of  the  constitution  of  the  plant  kingdom.  This  division 
recognized  no  connection  between  the  two  great  groups,  but  regarded 
them  as  wholly  distinct  in  origin  as  in  character.  But  the  rapid  ad- 
vances in  a  knowledge  of  plant  anatomy,  developed  toward  the  middle 
of  the  last  century,  and  especially  the  remarkable  and  epoch-making 
observations  of  Hofmeister  respecting  the  process  of  reproduction, 
enabled  him  to  break  down  the  old  barriers  erected  by  the  doctrine  of 
the  constancy  of  species,  and  prove  a  genetic  connection  between  the 
primary  divisions  of  Linnaeus.  With  this  starting-point,  the  crypto- 
gams and  the  phanerogams  were  subjected  to  a  severe  scrutiny  from  an 
entirely  new  point  of  view,  with  the  result  that  each  underwent  a  re- 
vision which  led  to  such  a  rearrangement  of  subdivisions  as  to  present 
an  entirely  fresh  conception  of  their  relations  to  one  another.  The 
logical  result  was  finally  expressed  in  the  subdivision  of  the  plant  world 
into  four  great  phyla,  which,  in  their  evolutional  sequence,  came  to  be 
known  as  I.,  Thallophyta;  II.,  Bryophyta;  III.,  Pteridophy ta ;  IV., 
Spermatophyta. 


THE  PALEONTOLOGIC  RECORD  69 

Admirable  as  this  scheme  is,  and  scientifically  acceptable  as  it  has 
proved  to  be,  it  nevertheless  presents  certain  well-recognized  defects 
with  respect  to  the  requirements  of  theory,  although  at  the  time  of  its 
formulation  and  as  late  as  1899  it  represented  the  sum  of  available 
knowledge.  It  was  just  at  this  time  that  paleobotany  became  available 
as  p,  means  of  meeting  those  deficiencies  which  a  knowledge  of  living 
^plants  could  not  overcome.  For  a  long  time  botanists  have  been  famil- 
iar with  certain  Paleozoic  remains  having  a  fern-like  aspect  which  were 
generally  accepted  as  ferns;  but  because  of  their  want  of  direct  con- 
nection with  stems  or  fruit,  there  remained  a  serious  doubt  as  to  their 
real  character.  In  the  same  horizons,  detached  fragments  of  stems 
were  also  observed  with  increasing  frequency.  The  study  of  their 
anatomy  disclosed  a  structure  which,  in  some  respects,  was  curiously 
like  that  of  ferns,  while  in  other  respects  it  approximated  to  the  anat- 
omy of  the  higher  plants  as  presented  in  some  of  the  gymnosperms. 
This  combination  of  filicinean  and  cycadean  characters  was  noted  by 
Potonie,  who  succeeded  in  correlating  them  and  expressing  their  phylo- 
genetic  position  in  the  name  of  a  new  order  which  he  called  the  Cyca- 
dofilices. 

There  yet  remained  to  be  considered  certain  remarkable  fruits  for 
which  no  relationship  has  as  yet  been  determined  until,  through  the 
work  of  Scott,  Oliver,  Kidston  and  others,  it  was  shown  that  they  were 
of  the  nature  of  seed-bearing  organs  which  could  be  correlated  with  the 
Cycadofilices.  It  thus  became  evident  that  there  was  a  hitherto  un- 
known group  of  plants  combining  the  characters  of  ferns  in  their  foli- 
age and  stem  structure  with  those  of  primitive  gymnosperms  as  pre- 
sented in  their  stems  and  fruits.  On  the  whole,  however,  these  plants 
approached  most  nearly  to  the  pteridophytes  in  their  external  features. 
To  this  new  phylum,  of  which  the  Cycadofilices  formed  the  most  con- 
spicuous member,  Scott  and  Oliver  in  1904  assigned  the  most  appropri- 
ate name,  Pteridospermae.  This  result  was  based  entirely  upon  paleon- 
tological  evidence  through  comparative  anatomy,  and  it  compels  us  to 
recognize  the  existence  of  five,  instead  of  four  great  phyla.  The  far- 
reaching  significance  of  this  achievement  can  not  be  overestimated.  It 
is  not  only  of  the  utmost  importance  as  proving  the  general  course  of 
evolution  and  bringing  into  the  realm  of  proved  facts  what  had  previ- 
ously been  a  working  hypothesis  only,  but  it  offers  an  entirely  new  point 
of  departure  for  the  botanist  of  the  future.  Attention  may  also  be 
directed  to  one  other  effect.  The  tendency  of  this  discovery  is  to  co- 
ordinate, unify  and  strengthen  all  branches  of  botanical  knowledge, 
bringing  to  us  the  conviction  that  the  more  extended  and  thorough  our 
knowledge  of  the  earlier  forms  of  vegetation  becomes,  the  more  satis- 
factory will  be  our  knowledge  of  the  science  as  a  whole;  for  while  the 
example  selected  is  probably  the  most  important  for  our  special  pur- 
poses, the  general  utility  of  paleontological  research  in  relation  to  the 


70  THE  PALEONTOLOGIC  RECORD 

history  of  development  is  enforced  upon  our  consideration  in  a  great 
many  subordinate  ways. 

Recognizable  plant  remains  first  occur  in  the  Silurian  in  the  form 
of  certain  highly  organized  algae,  the  ancestral  forms  of  which  are  un- 
known. Nevertheless,  the  history  of  NematopJiycus  shows  that  in  the 
Silurian  and  extending  through  the  Devonian,  members  of  the  brown 
algae  directly  comparable  with  the  modern  kelps,  both  in  general  char- 
acter and  in  detailed  structure,  had  attained  to  a  development  unknown 
to  any  of  the  marine  algae  of  to-day.  Arborescent  forms  with  stems  two 
feet  in  diameter  and  a  corresponding  height  lead  to  the  inference  that 
they  not  only  represent  the  culmination  of  the  phylum  at  that  time, 
but  that  they  must  have  been  preceded  by  a  long  line  of  ancestral  forms, 
extending  far  back  into  the  earlier  horizons,  possibly  into  the  Eozoic 
itself.  t 

Parka  decipiens  from  the  old  Red  Sandstone  of  Scotland  affords 
striking  illustration  of  the  very  early  period  at  which  heterospory  was 
developed  among  vascular  plants,  which,  according  to  the  evidence  now 
available,  are  comparable  with  the  genus  Marsilea  among  existing  types. 
In  these  remains  we  meet  with  prostrate  stems  often  one  to  two  inches 
in  diameter,  from  which  slender,  upright  branches  are  produced,  bear- 
ing in  turn  conceptacles  containing  both  micro-  and  mega-sporangia. 
Some  of  these  latter  further  contain  prothalli  in  various  stages  of  de- 
velopment. 

The  earliest  form  of  gymnosperm  is  that  which  we  recognize  in  the 
genus  Cordaites  from  the  Devonian.  The  highly  developed  and  dicoty- 
ledonous character  of  the  stem  affords  abundant  evidence  that  the 
ancestral  type  must  be  looked  for  in  some  remote  and  earlier  horizon, 
but,  taken  as  an  isolated  case,  it  affords  no  clue  whatever  to  the  origin 
of  that  particular  phylum,  although  the  subsequent  course  of  develop- 
ment may  be  traced  with  considerable  certainty  to  comparatively  recent 
times. 

The  obvious  conclusion  to  be  drawn  from  the  geological  relations 
presented  by  such  illustrations  as  those  recited,  is,  that  the  evolution  of 
even  very  simple  forms  from  the  most  primitive  plants  must  have 
called  for  enormously  lengthy  periods  of  time.  Even  the  most  liberal 
application  of  the  law  of  mutation  would  fail  to  adequately  account  for 
the  extensive  gaps  which  are  recognized  as  occurring  between  the 
simpler  types  and  those  which  lie  in  the  same  general  line  of  succes- 
sion, but  with  greatly  advanced  organization. 

We  are  now  led  to  ask,  how  far  have  paleontological  studies  carried 
us  in  our  knowledge  of  plant  life  from  the  earliest  times,  that  is,  do 
they  enable  us  to  trace  an  unbroken  series  of  steps  from  the  first  to  the 
last?  To  this  the  answer  must  be  that,  while  paleobotany  has  been  of 
the  greatest  service  in  supplying  missing  data,  in  filling  great  gaps  in  a 
supposed  sequence  and  in  giving  the  fullest  support  to  the  law  of  evo- 


THE  PALEONTOLOGIC  RECORD  71 

lution,  it  is  as  yet  by  no  means  adequate  with  respect  to  meeting  all  that 
theory  demands.  For  this  there  is  an  intelligible  explanation  based  in 
part  upon  the  fact  that  the  necessary  material  is  available  only  under 
conditions  of  great  difficulty;  and  that  the  character  of  the  remains 
upon  which  research  is  based  is  conditioned  by  the  original  nature  of 
the  t  structure  and  its  ability  to  survive  in  an  unaltered  form,  the  re- 
markable conditions  of  decay,  infiltration,  compression,  upheaval  and 
often  of  volcanic  influences  to  which  it  has  been  subjected.  The  earliest 
type  of  vegetation  was  that  which  we  now  find  in  hot  springs,  continued 
with  the  algae  found  in  cool  or  cold  waters,  all  of  which  possessed  a  deli- 
cacy of  structure  which  permitted  speedy  decay.  The  great  abundance 
of  such  organisms  probably  afford  an  adequate  explanation  of  the 
Laurentian  and  later  forms  of  graphite  which  is  regarded  by  many  as 
the  remains  of  former  vegetation.  While  this  hypothesis  may  be  ac- 
cepted provisionally,  paleobotany  is  nevertheless  wholly  unable  to  fur- 
nish any  clue  to  the  life  history  of  the  individuals,  or  even  to  inform 
us  as  to  the  specific  types.  Such  knowledge  as  we  possess  in  this  direc- 
tion is  the  result  of  inference  from  parallel  conditions  and  structures 
as  now  found. 

It  might  be  assumed  that  with  an  increasing  perfection  in  the  pres- 
ervation of  fossil  remains,  as  found  especially  in  the  later  formations, 
it  should  be  possible  to  trace  the  course  of  descent  with  accuracy  and 
completeness.  This  is,  in  a  measure,  true,  but  although  the  general  re- 
quirements of  theory  may  be  verified,  yet  the  haphazard  conditions 
involved  in  the  collection  of  plant  remains  make  it  a  very  difficult  mat- 
ter to  secure  a  complete  narrative,  and  there  remain  many  gaps  which 
it  is  difficult  to  fill.  The  evolutional  position  of  the  Bryophytes  de- 
mands that  the  origin  of  these  plants  should  lie  somewhere  in  the  early 
Silurian  or  even  in  the  Eozoic  age,  but  we  have  no  certain  knowledge 
of  them  until  the  middle  Mesozoic,  and  their  remains  do  not  become 
familiar  or  abundant  until  the  later  Tertiary.  So  important  a  devia- 
tion from  what  theory  demands  should  lead  us  to  caution  in  drawing 
conclusions  from  the  direct  testimony  which  is  thus  presented.  Unless 
otherwise  disposed  of  through  paleontological  evidence,  it  would  be 
more  correct  to  infer  that  the  delicacy  of  the  plants,  and  the  conditions 
of  their  fossilization,  have  not  admitted  of  their  preservation  in  a  recog- 
nizable condition ;  while  there  is  also  the  further  probability  that  many 
of  their  remains  have  been  overlooked  through  resemblance  to  certain 
Pteridophyta  for  which  they  might  well  be  mistaken. 

In  spite  of  such  apparent  contradictions,  the  evidence  everywhere 
points  with  great  force  to  the  idea  that  each  of  the  lesser  phyla  had  its 
origin  in  some  ancestral  form,  followed  by  growth  and  culmination. 
This  latter  was,  in  some  cases,  abrupt,  as  in  many  of  the  Pteridophytes ; 
in  other  instances  there  was  a- gradual  decline,  as  in  the  lycopods  or  the 
horsetails,  which  attained  their  highest  development  in  the  later  Paleo- 


72  THE  PALEONTOLOGIC  RECORD 

zoic,  but  have  since  been  in  a  state  of  degeneracy,  their  present  repre- 
sentatives being  few  in  number  and  of  a  depauperate  character.  The 
application  of  this  law  throughout  the  enormously  lengthy  periods  re- 
quired for  the  evolution  of  existing  species,  has  led  to  the  survival  of 
some  of  the  most  ancient  types  until  the  present  day;  to  the  absolute 
obliteration  of  others  which  at  one  time  gained  great  prominence;  and 
to  the  gradual  dying  out  of  yet  others,  some  of  which  are  now  found  in 
the  last  stages  of  their  existence.  But  through  the  entire  course  of 
change,  the  evolution  of  higher  and  yet  higher  forms  has  been  the  most 
conspicuous  fact.  Furthermore,  it  is  undoubtedly  true  that  the  general 
course  of  evolution  is  in  progress  to-day  as  in  the  past,  since  all  the 
potentialities  of  such  evolution  exist  now  as  always,  though  conditioned 
by  the  fact  that  owing  to  continued  changes  in  the  physical  character 
of  the  earth's  atmosphere  as  well  as  of  its  crust,  the  possibilities  of  evolu- 
tion are  steadily  diminishing  and  will  eventually  cease. 

There  is  one  direction  in  which  paleobotany  gives  well-defined  as- 
surance that  the  evidence  derived  from  existing  species  leads  to  correct 
conclusions.  In  tracing  the  succession  of  types,  we  are  led  to  the  belief 
that  there  is  no  direct  sequence.  Conterminous  evolution  is  in  accord 
with  neither  theory  nor  ascertained  facts,  and  it  is,  therefore,  impossible 
to  conceive  of  a  figure  which  shall  in  any  way  represent  a  single  and 
unbroken  line  of  succession.  If  paleontology  teaches  us  anything,  it  is 
that  each  great  phylum,  as  well  as  its  various  subdivisions,  finally  reaches 
its  culmination  in  a  terminal  member  from  which  no  further  evolution 
is  possible.  But  that  from  some  inferior  member,  possessing  high 
potentialities,  a  side  line  of  development  arises.  There  is  thus,  in  the 
early  life  of  each  member  of  the  series,  a  certain  recapitulation  of 
ancestral  characters.  This  conception  of  a  continuance  of  the  main 
line  of  descent  through  a  succession  of  lateral  members  is  both  logical 
and  fully  in  accord  with  the  evidence  derived  from  both  recent  and 
extinct  forms  of  plant  life,  as  well  as  with  our  present  theory  of 
evolution. 


PALEONTOLOGY  AND  ISOLATION 

BY  DR.  JOHN  M.  CLARKE 

STATE  MUSEUM,  ALBANY,   N.   Y. 

THE  notion  of  isolation  as  a  factor  in  variation,  as  I  am  using  the 
term,  is  that  of  geographic  separation  exclusively,  the  concep- 
tion expressed  most  clearly  by  Wallace,  Moritz  Wagner  and  Jordan. 
I  take  it  that  while  this  influence  has  been  carefully  estimated  in  the 
geographical  distribution  of  living  species,  it  has  not  often  been  ex- 
pressed in  its  own  terms  in  the  analysis  of  extinct  faunas.  With  in- 
creasing accuracy  in  the  record  of  ancient  continental  lines  and  bar- 


THE  PALEONTOLOGIC  RECORD  73 

riers,  we  are  coining  to  a  point  where  the  efficiency  of  this  factor  can 
be  safely  taken  into  account.  The  outcome  of  free  interbreeding,  as 
Jordan  has  pointed  out,  is  to  unify  species  and  obliterate  variations. 
Per  contra,  isolation  checks  this  process  and  gives  freer  play  to  tend- 
encies arising  from  other  factors  in  variation.  The  effect  is  thus,  as 
a  general  rule,  negative,  but  expresses  itself  freely  enough  in  geo- 
graphic provinces  severed  by  some  barrier  or  condition  which  has  the 
effect  of  a  barrier.  Among  existing  species  the  formative  effects  of 
segregation  have  been  very  largely  illustrated  from  restricted  areas 
such  as  the  subdivisional  valleys  and  forests  of  Hawaii  with  its  dis- 
tinctive forms  of  the  Helicidae  and  other  terrestrial  snails — a  case  that 
is  paralleled  in  paleontology  by  the  snails  of  Steinheim.  But  the  effect 
is  to  be  reckoned  with  in  larger  or  continental  areas  between  which 
there  has  been  at  one  time  opportunity  of  interchange,  especially  in 
the  case  of  marine  species,  with  which  we  chiefly  deal,  along  the  epi- 
continents. 

I  have  particularly  in  mind  phenomena  which  have  been  brought 
to  my  notice  by  a  somewhat  extended  study  of  the  Devonian  faunas 
of  the  southern  hemisphere  and  the  broader  application  of  the  factor 
is  best  enforced  and  illustrated  by  this  instance.  I  may  say  that  this 
broader  notion  seems  to  be  that  entertained  by  Darwin  so  far  as  he 
specified  the  conception  of  geographic  segregation  as  an  element  in 
natural  selection  and  it  was  his  work  in  South  America  that  formed 
the  basis  of  his  conclusions. 

With  other  students  we  recognize  the  existence  during  the  Devon- 
ian of  austral  continental  lands  which  have  been  variously  designated 
and  variously  outlined.  By  some  this  land  has  been  posited  as  a  north 
and  south  Atlantis  lying  in  the  meridional  axis  of  the  present  ocean, 
by  others  a  broken  land  mass  partly  crossing  the  southern  Atlantic 
from  east  to  west.  But  now  we  begin  to  see  its  continuity  and  the  ex- 
tent of  its  strands,  with  something  of  its  changes  in  outline  during 
its  early  history.  It  was  the  precursor  and  the  nucleus  of  Gondwana- 
land.  With  it  began,  so  far  as  we  now  know,  the  long  history  of  that 
continental  land  and  the  successive  records  of  life  developing  under 
continued  conditions  of  geographic  isolation  from  the  northern  strands. 

From  Argentina,  Bolivia  and  northern  Brazil  we  have  very  lucid 
evidence,  on  the  basis  of  paleontology,  that  in  the  late  Silurian  the 
shore  lines  were  continuous  with  those  of  the  north.  We  have  no  de- 
pendable knowledge  of  these  earlier  faunas  at  the  east  and  indeed 
their  entire  absence  is  indicated  by  stratigraphy;  but  with  the  sub- 
mergence of  the  Silurian  at  the  west,  there  entered  from  the  African 
east  upon  this  south  Atlantic  field,  a  positive  diastrophism  whose  axis 
was  well  nigh  normal  to  that  of  the  present  Atlantis,  and  along  the 
shores  of  this  growing  land  bridge  entered  an  invasion  of  marine  life 


74  THE  PALEONTOLOGIC  RECORD 

at  the  opening  of  the  Devonian  time.  It  seems  to  have  come  west- 
ward from  a  dispersion  area  in  Africa  and  it  evidently  disseminated 
itself  without  interruption  of  continuity  from  the  strands  which  now, 
as  the  Bokkeveld  beds  of  Cape  Colony,  constitute  the  only  evidence 
of  marine  life  in  the  South  African  Paleozoic,  to  those  of  the  Falkland 
Islands,  two  far  distant  regions  which  have  much  more  of  organic 
content  in  common  than  do  the  Falklands  and  the  nearer  regions  of 
Parana,  Argentina  and  Bolivia. 

This  fauna  with  its  special  and  peculiar  features  is,  however,  spread 
through  Bolivia,  western  Argentina,  southern  Brazil,  including  Parana 
and  as  far  north  as  Matto  Grosso,  thence  eastward  by  way  of  the  Falk- 
lands to  South  Africa.  From  the  boreal  strands  of  the  period  it  was 
separated  by  a  barrier,  often  narrow  and  constituted  only  of  deeper 
water,  so  that  of  the  boreal  Devonian  we  find  no  evidence  much  south 
of  the  equator  in  Brazil  nor  of  the  austral  Devonian  north  of  that  line. 
This  barrier  I  believe  to  have  been  overpassed  at  times  during  the  early 
part  of  the  Devonian  by  species  which  are  of  wider  distribution  south 
and  north  but  these  passages  seem  to  have  become  rarer  as  time  passed 
and  as  more  complete  geographic  isolation  was  effected. 

There  are  many  evidences  in  this  southern  fauna  that  the  land 
bridge  was  accompanied  by  insular  strands  which  are  evidenced  by 
varying  percentages  in  community  of  species  and  by  bathymetrical 
variations.  Apart  from  these  possible  island  masses,  there  was  clearly 
a  Devonian  land  bridge  extending  from  South  Africa  to  the  Falklands, 
westward  into  Argentina  and  northward  into  Bolivia,  embracing  also 
as  continental  or  island  lands  parts  of  the  states  of  Parana,  Matto 
Grosso  and  even  of  Para. 

By  virtue  of  the  evident  derivation  of  the  fauna  of  this  time  from 
the  east  along  newly  forming  strands  which  were,  throughout  the 
period  of  the  Devonian,  kept  asunder  from  the  Atlantic-European 
lands  at  the  north,  and  by  its  further  development  under  conditions 
of  isolation,  the  fauna  presents  fundamental  contrasts  to  any  develop- 
ment of  the  Devonian  elsewhere  in  the  world.  It  is  in  itself  a  unit  and 
a  unit  also  in  relation  to  the  sediments  in  which  it  is  involved.  There 
is  no  earlier  Devonian  in  this  southern  region  nor  is  there  any  later 
Devonian,  for  wherever  the  succession  has  been  determined  this  austral 
fauna,  bearing  no  evidence  in  itself  of  a  later  time  stamp  than  early 
Devonian,  is  overlain  by  Carboniferous  deposits  without  demonstrated 
unconformities  between.  Deposits  and  faunas  which  at  the  north  we 
are  accustomed  to  regard  as  of  later  Devonian  age,  are  absent  at  the 
south,  either  because  this  austral  land  was  broadly  above  the  sea  dur- 
ing these  stages  and  its  strands  now  lie  buried  or,  as  seems  much  more 
probable,  this  sedimentation  represents  the  total  Devonian  sedimenta- 
tion and  this  fauna  the  total  Devonian  fauna  at  the  south. 


TEE  PALEONTOLOGIC  RECORD  75 

I  can  not  in  this  place  analyze  the  peculiarities  which  give  the 
austral  fauna  of  these  "  Falklandia  "  strands  their  special  impress  but 
I  may  specially  cite  the  trilobites  which  are  astonishingly  developed. 
I  presume  any  competent  student  of  northern  faunas,  being  shown  a 
series  of  these  without  knowledge  of  their  origin,  would  pronounce 
them'  of  early  Devonian  age  and  yet  they  are  neither  northern  species 
nor,  in  any  large  degree,  northern  genera.  While  they  bear  the  im- 
press of  boreal  genera  and  resort  to  morphologic  equivalencies  thereto 
in  fugitive  epidermal  structures  which  so  richly  characterize  the  boreal 
trilobites  at  this  time,  they  are  on  the  whole  constructed  on  a  series  of 
modified  types  which  hold  their  fundamental  expression  while  de- 
veloping minor  details  with  the  chronology  normal  to  their  succession 
at  the  north.  The  Phacopes  are  seldom  true  PJiacopes,  the  Dalma- 
nites  seldom  true  Dalmanites,  yet  the  same  structural  decorations  and 
extravagances  we  are  familiar  with  at  the  north,  are  distributed  freely 
through  the  group.  This  is  all  equally  true,  in  qualifying  terms,  of 
the  other  groups  of  this  fauna,  save  for  the  fact  that  in  these  -we  can 
hardly  venture  to  insist  so  entirely  on  generic  distinctions  south  and 
north.  The  species  differences  declare  themselves  on  every  hand  and 
taken  as  a  whole  the  fauna  presents  fairly  conclusive  evidence  of  hav- 
ing derived  its  distinctiveness  through  its  isolation  from  the  boreal 
fauna  from  which  it  ancestrally  took  origin.  Yet  while  it  has  de- 
veloped this  character  it  has  also  proceeded  to  maintain  a  faunal  com- 
position which  declares  its  age,  and  a  morphological  stamp  which 
shows  that  it  developed  all  its  parts  in  the  proper  time  and  place  in  the 
series. 

In  predicating  geographic  isolation  as  the  prime  factor  in  this 
regional  development  of  the  Devonian  fauna,  its  efficiency  should  not 
be  made  to  seem  qualified  by  an  illustration  which  is  striking  by 
virtue  of  its  contrast  with  the  already  well  known.  There  are  evi- 
dences in  plenty  that  geographic  isolation  has  played  a  similar  role 
with  even  more  diverse  effect  in  the  development  of  the  boreal  faunas 
of  the  same  geologic  stage.  The  north  Atlantic  land  bridge  was  con- 
tinuous at  this  time,  as  evidenced  not  alone  by  the  presence  of  the 
Coblentzian  fauna  in  the  Atlantic  coast  rocks  but  by  an  array  of  addi- 
tional facts;  and  it  seems  very  probable  that  the  primary  movement  of 
these  northern  faunas  was  from  the  same  African  dispersion  area  as 
that  of  the  south. 


76          THE  PALEONTOLOGIC  RECORD 


THE  CONTINUITY  OF  DEVELOPMENT 

BY  DB.  W.  D.  MATTHEW 

AMERICAN   MUSEUM  OP  NATURAL  HISTORY 

/CONTINUITY  of  development  in  a  broad  sense  hardly  calls  for 
\-#  discussion  here.  The  paleontologic  evidence  in  its  favor  is  so 
extensive  and  so  universal  that  the  perfection  of  the  proof  is  merely  a 
question  of  the  completeness  of  the  evidence.  The  question  for  dis- 
cussion is  rather  as  to  the  method  of  race  development  and  specific 
change — whether  continuous,  by  the  slow  accumulation  of  minute  in- 
dividual variations,  definite  or  indefinite,  through  the  influence  of 
natural  selection  or  of  other  causes — or  discontinuous  by  the  sudden 
appearance  of  distinct  mutations  or  sports,  usually  of  subspecific  or 
specific  value,  sometimes  of  generic  value.  This  question  is  much  de- 
bated nowadays,  and  it  would  seem  that  the  evidence  from  paleontology 
ought  to  be  of  the  first  importance  in  deciding  it. 

It  is  very  commonly  asserted  that  this  evidence  is  strongly  in  favor 
of  discontinuous  development.  This  would  mean  that  new  species  and 
even  genera  appear,  as  a  rule,  suddenly  at  certain  levels,  and  that  the 
record  of  a  phylum  is  not  usually  a  slow  continuous  change  from  one 
species  into  another  as  we  pass  upward  from  stratum  to  stratum;  but 
that  one  species  has  a  certain  vertical  range  and  is  then  supplanted  by 
another  species,  this  in  turn  by  a  third,  and  so  on,  each  successive 
stage  being  an  advance  over  the  preceding,  but  the  species  overlapping 
instead  of  grading. 

I  think  that  there  is  no  question  but  that  in  vertebrate  paleontology 
the  evidence  taken  at  its  face  value  does  appear  to  be  very  distinctly 
in  favor  of  discontinuous  development.  Where  we  are  able  to  follow  a 
phylum  of  Tertiary  mammalia  through  a  series  of  strata  in  one  locality, 
we  find  that  the  successive  stages  appear,  as  a  rule,  full  formed  at  cer- 
tain levels,  supplant  and  replace  the  more  primitive  stages,  and  are  in 
turn  supplanted  and  replaced  by  more  advanced  stages.  In  former 
years,  when  the  records  of  locality  and  level  were  less  exact,  it  was 
possible  to  arrange  a  series  of  gradations  from  one  stage  to  another 
among  the  specimens  pertaining  to  a  particular  phylum,  and  to  assume 
that  this  gradation  corresponded  to  the  levels  in  the  formation  at 
which  the  specimens  had  been  collected,  and  that  the  specific  change 
was  through  continuous  gradation.  The  more  exact  records  of  locality 
and  level  and  the  more  extensive  and  complete  collections  in  recent 
years  have  in  general  failed  to  confirm  this  arrangement.  In  the  great 
majority  of  cases,  so  far  as  the  record  shows,  new  species  appear  already 


THE  PALEONTOLOGIC  RECORD  77 

distinct,  at  first  sporadically  along  with  the  more  primitive  ones,  then 
more  abundantly,  finally  replacing  the  older  ones  altogether.  The 
intermediate  gradations  occur  along  with  the  more  typical  individuals, 
but  without  much  definite  relationship  to  intergradation  in  the  succes- 
sion of  strata.1 

We  may  illustrate  from  the  evolution  of  the  oreodonts,  as  these  are 
the  most  abundant  and  most  completely  known  of  American  fossil 
mammals. 

The  earliest  known  representatives  of  the  phylum  are  Protoreodon 
and  Protagrioclicerus  from  the  Upper  Eocene  Uinta  beds  of  Utah.  Both 
have  very  short  crowned  teeth  with  five  crescents  on  the  upper  molar,  the 
fifth  crescent  quite  distinct.     The  fourth  premolar  is  not  molariform. 
For  the  next  stage  we  have  to  shift  to  another  formation,  400  miles 
away,  the  White  Eiver.     In  the  lowest  strata  of  this  formation,  the 
Titanotherium  beds,  we  find  Oreodon,  Bathygenys  and  Agriochcerus, 
all  with  decidedly  longer  crowned  teeth,  and  no  trace  of  the  fifth  cres- 
cent in  the  molars.     In  Oreodon  and  Bathygenys  the  fourth  premolar 
is  non-molariform,  composed  of  one  inner  and  one  outer  crescent,  as 
usual  among  Artiodactyls.     In  Agriochcems  it  has  become  imperfectly 
molariform  with  two  outer  crescents  and  one  inner  one.    Between  the 
Uinta  and  White  River  oreodonts  a  sharp  break  intervenes  and  no 
intermediates  are  known.     From  this  point  we  can  trace  the  subphyla 
of  oreodonts  up  through  a  considerable  succession  in  the  Big  Badlands 
of  South  Dakota  and  the  adjoining  region.     Oreodon  culbertsoni,  0. 
bullatus,  Eucrotaphus,  Eporeodon,  Mesoreodon  and  Merychyus  appear 
to  be  approximately  successive  stages  in  specialization.     The  skull  is 
shortened,  the  teeth  become  longer  crowned,  the  tympanic  bullse  are 
enlarged,  lachrymal  vacuities  appear,  the  limbs  are  lengthened,  the 
feet  lengthened  and  compacted  and  the  thumb  is  lost.     But  there  is 
not  a  continuous  intergradation  in  any  of  these  features  as  we  pass 
upward  in  the  beds.     Oreodons  with  small  bullse  are  abundant  in  the 
lower  and  middle  White  Eiver,  the  bullae  varying  very  little  in  size. 
A  species  with  medium-sized  bullse  occurs  occasionally  associated  with 
them.    In  the  Upper  White  River  all  the  oreodons  that  I  have  seen  have 
bullae  of  large  size.    The  size  of  the  bulla,  then,  does  not  increase  con- 
tinuously as  we  go  up  through  the  formation.     Another  and  much 
more  specialized  genus  of  oreodonts,  Leptauclienia,  suddenly  appears 
in  abundance  in  the  Upper  White  River.    I  have  seen  a  single  specimen 
of  this  genus  from  the  Middle  beds,  but  it  shows  no  more  primitive 
features  than  those  of  the  Upper  beds.    In  the  Lower  Rosebud,  immedi- 
ately overlying  the  White  River,  species  of  Eporeodon  are  common,  like 
1  The  statements  of  fact  herein  contained  are  based  partly  upon  field  experi- 
ence, chiefly  upon  the  records  of  some  20,000  specimens  of  fossil  mammals  and 
reptiles  in  the  American  Museum  collections,  most  of  which  the  writer  has  had 
occasion  to  examine  and  identify  and  to  post  the  field  records   of  level  and 
locality,  in  the  course  of  cataloguing  work. 


78  THE  PALEONTOLOGIC  RECORD 

those  of  the  underlying  beds  except  that  some  of  them  have  well-de- 
veloped lachrymal  vacuities  while  others  have  none.  Another  new  race 
also  makes  its  appearance  suddenly,  and  in  great  abundance,  in  the 
genus  Promerycochcerus — structurally  derivable  perhaps  from  some 
of  the  older  oreodons,  but  not  connected  with  them  by  intergrada- 
tions.  Agriochcerus  has  disappeared.  In  the  Upper  Rosebud  the 
Oreodon-Merycliyus  phylum  shows  a  distinct  and  marked  advance  in 
the  length  of  the  crowns  of  the  teeth;  lachrymal  vacuities  are  always 
present,  the  feet  are  decidedly  more  compact  and  elongate.  Promery- 
cochoerus  disappears  entirely  and  is  replaced  by  a  very  distinct  and 
more  advanced  genus  Merycochoerus.  The  Leptauchenia  series  has  dis- 
appeared temporarily,  to  re-appear  in  the  Middle  Miocene  in  a  more 
specialized  genus,  Cyclopidius,  the  last  known  member  of  this  race. 

The  Middle  Miocene  (which  should  follow  the  Upper  Rosebud)  is 
unrepresented  at  the  locality  under  consideration  (Pine  Ridge,  South 
Dakota),  but  elsewhere  overlies  beds  with  an  equivalent  fauna,  and 
contains  Merycochoerus  in  one  locality  with  Merychyus  (both  repre- 
sented by  more  specialized  species) ;  in  another  locality  it  contains 
instead,  Promerycochcerus  with  Ticholeptus  (allied  to  Merychyus)  ;  in  a 
third  is  found  the  most  highly  specialized  member  of  the  Merycochoerus 
line,  Pronomotherium.  In  the  Upper  Miocene  and  Lower  Pliocene  the 
oreodonts  become  much  scarcer,  and  the  skulls  and  skeletons  are  known 
only  in  two  or  three  instances.  Pronomotherium  certainly  occurs  in 
Montana;  in  Nebraska  the  Merychyi  are  more  advanced  in  dentition, 
belonging  to  a  distinct  subgenus  Metoreodon;  but  whether  the  skulls 
and  skeletons  are  equally  different  we  do  not  yet  know,  nor  are  we  in 
a  position  to  say  whether  the  change  is  gradual  or  saltatory. 

But  the  sum  of  results  in  regard  to  the  changes  from  one  stage  to 
another  in  this  best  known  group  of  fossil  mammals  is  either  that  the 
changes  are  abrupt,  constituting  clean-cut  faunal  divisions  marked  by 
the  sudden  appearance  in  abundance  of  a  more  advanced  stage;  or  else 
that  the  new  form  replaces  the  older  one  little  by  little,  but  on  the 
whole  can  not  be  fairly  said  to  be  gradually  converted  into  it  by 
infinitesimal  gradations. 

This  general  observation  applies,  in  my  opinion,  equally  well  to  any 
abundant  group  of  fossil  vertebrates  whose  phylogeny  is  sufficiently 
known  to  make  them  worth  considering. 

If,  therefore,  we  consider  that  the  record  is  continuous  where  there 
is  no  apparent  stratigraphic  break,  and  that  the  known  record  really 
represents  what  was  going  on  over  the  entire  continent  of  North 
America,  I  do  not  see  that  we  can  fairly  escape  from  the  conclusion  that 
new  species,  new  genera  and  even  larger  groups  have  appeared  by  salta- 
tory evolution,  not  by  continuous  development. 

But — and  here  lies  the  crux  of  the  whole  question — we  have  no 


THE  PALEONTOLOGIC  RECORD  79 

right  whatsoever  to  make  either  of  these  assumptions.  And  without 
them  the  argument  from  paleontology  for  discontinuous  development 
is  almost  or  quite  worthless. 

If  we  consider  the  general  conditions  controlling  evolution  and 
migration  among  land  mammals,  it  will  be  evident,  I  think,  that — 

1.  The  external  conditions  favoring  the  evolution  and  progress  of  a 
given  phylum  will  not  be  uniformly  developed  all  over  the  world  or 
all  over  one  continent,  but  will  appear  first,  and  be  at  all  times  more 
advanced,  in  some  circumscribed  region  in  one  or  another  continent,  or 
simultaneously  in  limited  areas  of  two  or  more  continents,  similarly 
situated  as  to  climate,  temperature,  etc. 

2.  The  animal  best  able  to  take  advantage  of  these  conditions  will 
be  existing  at  the  time  (a)  in  one  continent  or  (&)  in  more  than  one, 
or  (c)  different  animals  in  different  continents  may  be  equally  able  to 
adapt  themselves  to  the  new  conditions. 

3.  As  a  result,  the  new  stages  of  any  progressive  race  will  first  appear 
in  a  limited  area  and  will  spread  out  from  that  region  as  the  favoring 
environment  spreads,  the  race  at  the  same  time  continuing  its  progress 
further  within  that  area.     This  area  will  be  the  center  of  dispersal  of 
the  race.      Its  location  will  be  conditioned  by  two  factors,  the  early 
appearance  of  the  new  environmental  conditions,  and  the  existence  of 
species  most  able  to  take  advantage  of  these  conditions.     Parallelism 
and  convergence  in  racial  evolution  will  be  conditioned  by  2b  and  2c 

4.  Progressive  change  from  uniformly  warm  to  zonal  climates  dur- 
ing the  Tertiary  must  needs  have  been  a  great  factor  in  controlling  the 
progress  and  distribution  of  Tertiary  mammals.     As  the  new  conditions 
appeared  first  at  the  poles,  the  chief  centers  of  dispersal  of  the  animals 
adapted  to  them  must  have  been  in  the  northern  parts  of  one  or  another 
of  the  great  northern  continents.2    The  exact  location  of  the  dispersal 
center  for  each  race  would  be  variously  decided  by  the  complex  of 
environmental  and  faunal  relations  of  each,  and  might  be  shifted  from 
time  to  time  by  changes  in  these  relations. 

5.  In  the  regions  distant  from  the  center  of  dispersal  the  geological 
record,  if  complete,  should  show  the  successive  appearance  of  progres- 
sively higher  types  in  a  phylum,  arriving  in  successive  waves  of  migra- 
tion, and  each  new  type  suddenly  or  gradually  displacing  the  previous 
stages.     Whether  the  evolution  of  a  race  at  its  center  of  diffusion  was 
continuous  or  discontinuous,  the  geological  record  of  its  progress  pre- 
served in  any  other  region  would  be  apparently  that  of  a  discontinuous 
development.     It  would  be  not  the  actual  history  of  its  evolution  but 

2  To  a  minor  extent  in  the  southern  parts  of  the  southern  continents,  whose 
restricted  area  and  isolation  prevailed  in  the  writer's  opinion  throughout  the 
Tertiary.  There  is  some  evidence,  however,  along  the  lines  indicated  in  para- 
graphs 5  and  6,  that  Patagonia  was  the  chief  center  of  dispersal  of  South 
American  Tertiary  mammals. 


8o  THE  PALEONTOLOGIC  RECORD 

an  approximation  to  it.  The  closeness  of  the  approximation  would  be 
largely  measured  by  the  nearness  and  accessibility  of  the  region  in 
question  to  the  center  of  dispersal  of  the  race. 

6.  If  the  evolution  at  the  center  of  dispersal  was  sharply  discon- 
tinuous this  discontinuity  would  be  merely  emphasized  elsewhere.     If 
on  the  other  hand  it  was  continuous,  we  should  get  a  near  approach 
to  continuity  in  a  complete  evolutionary  series  from  a  region  not  remote 
from  the  center  of  diffusion  of  the  race,  while  the  evolutionary  series 
from  the  same  region,  of  a  race  whose  center  of  dispersal  was  remote, 
would  be  sharply  discontinuous. 

7.  Applying  these  principles  to  some  of  our  American  Tertiary 
phyla,  we  find  that  certain  phyla  which  we  can  be  sure  were  of  North 
American  origin,  such  as  the  camels,  oreodonts  and  peccaries,  do  present 
a  much  nearer  approach  to  continuity  of  development  than  do  other 
phyla  which  we  can  be  sure  were  of  old  world  origin,  such  as  the  deer, 
the  antelopes  or  the  proboscideans. 

I  assume  that  since  the  oreodonts  and  peccaries  never  reached  the 
old  world,  and  the  camels  did  not  reach  it  till  the  Pliocene,  their  centers 
of  dispersal  were  well  to  the  south  of  the  Bering  Sea  connection  with 
the  old  world.  I  assume  that  since  the  horses  are  represented  by  a 
double  evolutionary  series,  one  in  Europe,  a  closer  one  in  North  America, 
their  center  of  dispersal  lay  far  enough  north  to  spread  into  Europe 
on  one  hand,  North  America  on  the  other,  but  that  the  latter  was 
nearer  or  more  accessible,  i.  e.,  their  center  of  dispersal  was  north- 
eastern Asia  or  Alaska.  On  similar  grounds  the  center  of  dispersal  of 
most  of  the  Tertiary  ruminants  might  be  located  in  northwest  Asia,  of 
proboscideans  in  central  Asia,  of  tapirs  in  northeastern  Asia,  of  rhi- 
noceroses northeast  Asia  and  Alaska,  of  dogs  in  northwest  Canada,  and 
so  on — a  series  of  indefinite  guesses  which  a  careful  study  of  the  present 
geographic  distribution,  with  these  principles  and  the  imperfect  geologic 
data  in  mind,  might  serve  to  fix  more  definitely. 

The  point  at  present  to  be  considered  is  that  in  such  series  as  the 
camels,  oreodonts  and  peccaries,  we  do  have  a  sufficiently  close  approach 
to  a  continuous  series  to  warrant  our  believing  that  the  true  process  of 
their  evolution  in  the  center  of  their  dispersal  was  a  gradual  one  as 
regards  the  evolution  of  genera  and  higher  groups,  but  for  aught  that 
paleontology  tells  to  the  contrary,  it  may  have  been  partly,  though  not 
wholly,  discontinuous  and  saltatory  so  far  as  the  evolution  of  new  species 
is  concerned.  But  the  larger  and  more  complete  the  series  of  speci- 
mens studied,  the  more  perfect  the  record  in  successive  strata,  and  the 
nearer  is  the  hypothetic  center  of  dispersal  of  the  race,  the  closer  do 
we  come  to  a  phyletic  series  whose  intergrading  stages  are  well  within 
the  limits  of  observed  individual  variation  in  the  race.  The  known 
facts  in  vertebrate  paleontology  are,  in  my  opinion,  utterly  inadequate 


THE  PALEONTOLOGIC  RECORD  81 

to  prove  whether  the  development  of  races  was  or  was  not  wholly  con- 
tinuous. But  I  think  that  the  evidence,  considered  in  relation  to  the 
imperfection  of  our  knowledge,  goes  to  show  that  the  gaps  were  not 
normally  wide.  In  exceptional  cases  I  think  we  have  reason  to  believe 
that  they  were  wide  (Otocyon,  for  instance),  but  in  these  instances  the 
evidence  is  not  that  of  the  paleontological  record. 


THE  CONTINUITY  OF  DEVELOPMENT 

BY  DB.  T.  WAYLAND  VAUGHAN 

U.   S.  GEOLOGICAL  SURVEY 

AS  nearly  every  one  now  admits  the  validity  of  the  arguments  in 
favor  of  the  derivations  of  the  existing  groups  of  organisms  from 
previous  somewhat  different  organisms  through  the  operation  of  nat- 
ural causes,  I  will  not  enter  upon  a  discussion  of  the  truth  of  the 
theory  of  organic  evolution,  nor  will  I  present  the  results  of  phylo- 
genetic  studies.  We  will  assume  evolution  to  be  true,  and  having  made 
this  assumption,  the  theories  of  the  process  and  the  underlying  causes 
may  be  discussed. 

Only  two  theories  of  the  process  of  evolution  seem  to  me  possible: 
(1)  Darwin's  theory  of  gradual  transformation,  or  the  origin  of  new 
species  by  the  gradual  augmentation  through  successive  generations  of 
the  difference  between  progeny  and  ancestors;  (2)  that  brought  par- 
ticularly into  prominence  by  de  Yries,  the  theory  of  saltation,  called  by 
him  mutation,  according  to  which  the  progeny  differs  definitely,  with- 
out intergradation,  from  the  parents,  and  the  difference  is  perpetuated 
by  heredity.  There  are  two  theories  of  the  cause  of  evolution.  Accord- 
ing to  the  first,  that  of  "Weismann,  the  cause  is  within  the  organisms 
themselves,  new  kinds  being  produced  by  an  inherent  tendency  to  vary, 
this  tendency  being  due  to  differences  in  the  germ  cells  of  the  two 
parents;  the  second  theory  attributes  the  cause  to  the  action  of  the 
environment  on  the  organisms  inhabiting  it. 

The  fundamental  problems  of  evolution  can  then  be  resolved  into 
two  questions.  Is  evolution  through  gradual  divergence  from  the 
parental  type,  or  by  saltation ;  and  is  it  caused  merely  by  the  differences 
in  the  parental  germ-plasms  or  is  heritable  variation  produced  by  the 
environment  acting  on  the  organisms  ? 

As  we  are  all  paleontologists,  the  question  may  appropriately  be 
put,  what  light  can  paleontology  throw  on  these  problems?  It  may 
perhaps  render  some  assistance  in  deciding  between  gradual  transforma- 
tion and  saltation,  when  superimposed  conformable  beds  contain  suffi- 
ciently abundant  faunas,  and  perhaps  the  Tertiary  marine  formations 
of  our  southern  states  will  yield  important  results  when  studied  in 


82  THE  PALEONTOLOGIC  RECORD 

proper  detail.  Dr.  Dall  has  already  traced  more  or  less  completely  the 
genealogy  of  some  of  the  species,  and  I  have  noticed  certain  series  of 
species — the  group  of  Corbula  fossata,  C.  oniscus,  C.  wailesiana,  etc., 
being  one  of  them — deserving  thorough  study,  but  the  paleontologic 
work  known  to  me  has  not  as  yet  been  done  with  the  requisite  detail  to 
form  the  basis  of  an  opinion.  The  principal  contribution  to  our  gen- 
eral knowledge  of  the  evolution  of  organisms  that  paleontology  can 
make,  however,  is,  I  believe,  in  tracing  out  phylogenetic  lines,  and  I 
believe  the  discovery  of  the  processes  and  causes  of  evolution  must  rest 
with  the  experimental  biologist.  During  the  past  few  years  very  im- 
portant experimental  investigations  have  been  made  by  several  men, 
and  I  venture  to  refer  to  their  results,  as  I  regard  paleontology  as  only 
an  aspect  of  biology,  and  think  the  students  in  that  field  should  utilize 
the  information  gleaned  in  others. 

In  the  study  of  variation  it  has  been  shown  that  the  selection  of 
fluctuating  variations  does  not  carry  the  species  beyond  a  certain  limit, 
or  the  extent  of  the  variation  is  limited,  leading  to  the  conclusion  that 
new  species  can  not  be  produced  by  this  method.  I  may  here  refer  to 
ecological  surveys  and  the  unreliability  of  conclusions  reached  by  such 
researches.  Dr.  Merriam  several  years  ago  presented  a  paper  "  Is  Mu- 
tation a  Factor  in  the  Evolution  of  the  Higher  Vertebrates  ?"  in  which 
he  announced  the  conclusion  that  it  was  not.  A  critical  examination  of 
Dr.  Merriam's  data  showed  he  had  not  sufficient  information  on  which 
to  base  such  a  conclusion.  His  data  possess  value  for  the  study  of  evo- 
lution in  that  they  indicate  material  that  may  be  profitably  investigated 
by  the  experimental  method.  Attention  should  also  be  called  to  the 
probable  insufficiency  of  conclusions  reached  by  studying  material  from 
successive  geologic  horizons.  For  instance,  suppose  that  two  usually 
distinct  forms  are  connected  by  intermediates.  There  are  no  means  of 
ascertaining  whether  the  intermediates  represent  transition  stages  be- 
tween the  two  forms  or  are  examples  of  blended  hybridism. 

That  new  species  may  originate  through  saltation  is  rather  definitely 
proved ;  but  that  it  is  the  only  process  is  not  established. 

To  consider  the  causes  of  the  origin  of  new  forms :  That  new  forms 
should  originate  from  the  old  without  the  action  of  some  new  influence 
seems  to  me  impossible.  The  circle  of  possible  combinations  of  already 
existent  characters  could  not  be  transcended,  and  there  would  result  by 
crossing  only  all  the  combinations  possible  within  definite  limits;  this 
would  be  especially  obvious  if  the  de  Vries  hypothesis  of  unit-characters 
be  true.  Many  experiments  to  determine  the  influence  of  various  phys- 
ical factors  on  individuals  showed  only  somatic  changes  not  of  heritable 
nature  and  the  data  accumulated  seem  definitely  to  prove  that  somatic 
changes,  or  acquired  characters  induced  through  the  soma,  are  not  in- 
herited. 


THE  PALEONTOLOGIC  RECORD  83 

Weismann  made  a  great  contribution  to  the  progress  of  biology  by 
focusing  attention  on  the  germ  cells,  and  although  many  of  his  specula- 
tions may  be  discarded,  he  was  a  great  stimulator  of  thought.  The  work 
of  MacDougal  and  Tower  seems  to  show  how  the  environment  may  act 
on  the  individual  through  the  germ-cells  and  induce  permanent  changes 
in  the  progeny. 

MacDougal  has  experimented  with  species  of  evening-primroses,  by 
injecting  salt  solutions  into  the  seed  capsules,  and  summarizes  his  con- 
clusions in  two  paragraphs  i1 

The  action  of  reagents  having  an  osmotic  and  a  chemical  effect  has  resulted 
in  the  induction  of  mutants  in  the  progeny  of  Raimannia  odorata  and  (Enothera 
biennis.  The  mutants  thus  induced  have  been  tested  to  the  second  and  third 
generation  and  found  to  come  true  to  their  newly  assumed  characters. 

The  induction  of  mutants  by  the  action  of  reagents  is  a  conclusive  demon- 
stration of  the  fact  that  hereditary  characters  may  be  altered  by  external  forces 
acting  directly  upon  the  reproductive  mechanism.  The  action  of  the  reagents 
used  experimentally  is  simulated  by  many  conditions  occurring  in  nature. 

Tower  has  conducted  a  series  of  experiments  on  species  of  beetles 
belonging  to  the  genus  Leptinotarsa.  He  endeavored  to  influence  de- 
velopment by  the  conditions  of  moisture  and  temperature  during  the 
germinal  stages,  and  induced  changes  that  were  perpetuated  in  the  off- 
spring, the  changed  offspring  at  least  in  some  instances  mendelizing 
with  the  parent  species.  He  presents  his  conclusions  in  the  following 
words  :2 

A  careful  consideration  of  the  various  lines  of  experimentation  recorded 
and  of  the  pedigree  cultures  and  the  data  from  observations  in  nature  irre- 
sistibly forces  one  to  the  conclusion  that  in  these  beetles  the  only  variations  of 
permanence  are  germinal,  and  that  evolution  is  through  germinal  variations. 
Those  germinal  variations  which  arise  in  nature  are  permanent  and  the  same 
variations,  of  the  same  degree  of  permanence,  are  produced  in  experiment.  The 
diverse  kinds  of  evidence  produced  in  this  and  in  preceding  chapters  all  go  to 
show  that  under  varying  conditions  of  their  surroundings  these  beetles  vary, 
and  that  as  they  become  more  and  more  extreme  an  increasing  percentage  of 
striking,  permanent  variations  is  found;  and  as  I  have  just  shown,  it  is  possible 
in  experiment  to  produce  in  this  same  way  a  variety  of  permanent  modifications. 
From  all  this  evidence,  however,  there  nowhere  appears  the  least  trace  of  a 
suggestion  of  any  specific  action  of  the  conditions  of  existence,  but  everywhere 
there  appears  only  the  action  of  environment  as  a  stimulus,  while  the  response 
is  entirely  determined  by  the  organism.  All  of  these  variations  of  purely  tem- 
porary and  of  permanent  kinds  resolve  themselves  into  responses  of  the  organism 
to  the  stimuli  of  its  environment,  but  the  nature  of  the  response  is  entirely 
determined  within  the  organisms.  It  is  true  that  different  intensities  of  the 
same  stimuli  call  forth  different  responses,  but,  as  is  shown  in  the  chapter  on 

^'Mutations,  Variations  and  Relationships  of  the  (Enotheras,"  Carnegie 
Institution  of  Washington,  No.  81,  p.  90,  1907. 

a"An  Investigation  of  Evolution  in  Chrysomelid  Beetles  of  the  Genus 
Leptinotarsa,"  Carnegie  Institution  of  Washington,  Publication  No.  48,  p.  295, 
1906. 


84  THE  PALEONTOLOGIC  RECORD 

coloration,  the  response  is  entirely  determined  within  the  organism,  which  is 
adjusted  to  different  intensities  of  stimuli  and  reacts  according  to  its  own 
method  and  on  the  basis  of  its  own  constitution,  there  being  no  specific  reaction 
called  forth  by  a  given  stimulus. 

I  conclude  in  the  light  of  these  experiments  that  the  production  of  heritable 
variations,  slight  or  extreme,  represents  in  these  beetles  the  response  of  the 
germ  plasm  to  stimuli.  In  my  experiments  these  stimuli  were  external,  but 
there  is  no  a  priori  reason  why  they  might  not  also  be  internal. 

I  desire  also  to  call  your  attention  to  some  remarks  by  Loeb  :3 

It  is  obvious  that  no  theory  of  evolution  can  be  true  which  disagrees  with 
the  fundamental  facts  of  heredity.  It  is  the  merit  of  de  Vries  to  have  shown 
that  a  mutation  of  species  can  be  directly  observed  in  certain  groups  of  plants, 
and  he  has  further  shown  that  the  changes  occur  by  jumps,  not  gradually.  This 
fact  harmonizes  with  the  consequence  to  be  drawn  from  Mendel's  experiments 
that  each  individual  characteristic  of  a  species  is  represented  by  an  individual 
determinant  in  the  germ.  This  determinant  may  be  a  definite  chemical  com- 
pound. The  transition  or  mutation  from  one  form  into  another  is  therefore 
only  possible  through  the  addition  or  disappearance  of  one  or  more  of  the 
characteristics  of  determinants.  If  this  view  can  be  applied  generally,  it  is 
just  as  inconceivable  that  there  should  be  gradual  variation  of  an  individual 
characteristic  and  intermediary  stages  between  two  elementary  mutations,  as 
that  there  should  be  gradual  transitions  between  one  alcohol  and  its  next 
neighbor  in  a  chemical  series. 

To  summarize  my  own  opinions  on  this  subject : 

1.  I  think  it  very  doubtful  if  paleontology  can  make  any  especially 
valuable  contribution  to  our  knowledge  of  the  process  or  causes  of  the 
evolution  of  organisms,  and  that  this  field  must  be  surrendered  to  the 
experimental  biologist. 

2.  The  results  of  experimental  work  indicate  that  the  process  is  not 
by  the  gradual  transformation  of  species,  but  by  saltation.     However, 
the  former  method  has  not  been  shown  impossible. 

3.  Experimental  investigations  also  indicate  that  the  cause  of  evo- 
lution is  by  the  environment  acting  on  an  organism  capable  of  respond- 
ing to  it. 

4.  The  causes  of  evolution  are  chemical  in  their  nature,  and  the  aid 
of  the  chemist  is  necessary  for  their  thorough  elucidation. 

« "  The  Dynamics  of  Living  Matter,"  p.  3,  1906. 


THE  PALEONTOLOGIC  RECORD  85 


THE    BIRTHPLACE    OF   MAN 

BY  PBOFBSSOB  S.  W.  WILLISTON 

THE    DNIVEKSITT   OP   CHICAGO 

ARIOUS  writers,  from  Le  Conte  to  Smith  Woodward,  have  spoken 
V  of  critical  or  rhythmical  periods  in  evolution,  periods  when  evo- 
lutionary forces  have  acted  more  vigorously  than  at  others,  with  inter- 
vals of  relative  quiescence.  What  these  forces  are  and  have  been  we 
are  not  yet  sure,  whether  extrinsic,  that  is,  environmental  or  Lamarck- 
ian,  or  intrinsic,  that  is,  orthogenetic,  teleological  or  what  not.  Per- 
haps we  shall  sometime  be  more  certain  of  the  basal  causes  of  evo- 
lution, for  the  paleontologist  at  least  is  not  satisfied  with  the  crass 
ignorance  of  our  Weismannian  friends  who  impute  the  beginning  of  all 
things  to  mere  chance.  Perhaps  when  we  do  know  these  fundamental 
causes  we  shall  understand  better  why  evolution  has  been  rhythmical, 
if  such  was  really  the  case,  as  some  of  us  believe  with  Woodward. 

But,  whether  there  have  been  internal  forces  which  have  had 
chiefly  to  do  with  the  rhythm  of  evolution,  or  whether  such  critical 
periods  in  the  evolution  of  organic  life  have  been  due  solely  to  the 
larger  cosmic  forces,  I  think  we  shall  all  admit  that  there  have  been 
critical  places  of  organic  evolution,  places  upon  the  earth  where  evolu- 
tion has  advanced  with  more  rapid  pace  than  in  others,  places  per- 
haps where  environmental  conditions  have  conspired  to  hasten  the  de- 
velopment of  life,  or  of  particular  groups,  classes  or  kingdoms  of  life. 

Such  a  critical  period,  at  least  for  the  higher  organisms,  it  seems  to 
me,  was  the  early  Pliocene ;  such  a  critical  place  was  central  Asia ;  and 
both  together  resulted  in  the  birth  of  man. 

It  is  a  curious  fact  that  nearly  all  our  domestic  animals  had  their 
origin  in  Asia.  It  is  also  a  curious  fact  that  the  domestic  animals  are, 
almost  without  exception,  the  crowning  ends  of  their  respective  lines 
of  descent,  the  most  highly  specialized  of  their  kinds.  The  genus  Bos, 
the  most  highly  developed  of  the  even-toed  ungulates  began,  to  the 
best  of  our  present  knowledge,  in  the  Lower  Pliocene  of  India.  And 
its  four  distinctive  types  likewise  first  appeared  there:  the  Bubalus 
group,  including  the  domestic  buffalo  of  India,  and  its  untamable  kin 
of  Africa;  the  group  that  is  represented  by  the  domesticated  humped 
oxen  of  India  and  their  wild  relatives  of  Africa ;  the  bison  strain  which 
spread  in  Pleistocene  times  almost  to  the  remote  corners  of  the  earth; 


86  THE  PALEONTOLOGIC  RECORD 

and  the  true  oxen,  the  most  useful  of  all  creatures  to  man,  which 
spread  to  Europe  as  Bos  primigenius,  the  ancestor  of  Bos  taurus. 

The  sheep  also  found  their  expression  point  in  India,  and  their 
home  to-day  is  central  Asia.  So  too  the  domestic  goat  yet  lives  wild  in 
western  Asia,  a  less  plastic  type,  but  purely  Asiatic  in  origin.  Indeed, 
of  the  whole  family  of  Bovidse,  Asia  was  the  origin  and  dispersal  center, 
and  it  is  a  curious  fact  that  it  still  remains  the  home  of  the  higher 
types  while  others  of  lower  degree  have  wandered  afar  to  find  their 
homes  in  Africa,  Europe  and  America.  The  camelids  after  long  ages 
of  exclusive  development  in  North  America  migrated  to  Asia  to  find 
their  highest  evolution  in  the  true  camels,  the  highest  and  probably 
final  stage  in  the  evolution  of  the  family,  while  their  kin,  of  lower  de- 
gree, went  southward  to  terminate  in  the  llama  and  alpaca,  the  only 
mammals  among  all  man's  servants  which  we  can  say  with  tolerable 
certainty  have  been  entirely  beyond  the  influence,  direct  or  indirect,  of 
Asiatic  environment.  The  reindeer,  the  highest  of  all  the  cervid  fam- 
ily, doubtless  arose  in  northern  Asia;  certainly  its  home  is  in  part 
there,  though  some  of  its  early  kin  migrated  to  America  and  have  left 
their  descendants  in  the  caribous.  And  India  was  the  birthplace,  as  it 
is  the  home,  of  the  pig,  whence  came  originally  our  domesticated  swine. 
Whether  or  not  we  give  to  Sus  the  highest  place  among  the  non-rumi- 
nant, even-toed  ungulate  mammals,  or  to  the  Babirussa,  matters  not, 
for  both  are  of  Asiatic  origin. 

Of  the  odd-toed  ungulates  our  domestic  horse,  Equus  cdballus, 
stands  on  the  very  summit;  and  Equus  caballus  arose  in  Asia,  where 
its  ancestors  yet  have  their  wild  progeny.  And  I  believe  that  eventually 
we  must  give  to  Asia  the  honor  of  the  birthplace  of  the  genus  itself. 
And  the  next  lower  type  of  the  Equidse,  the  asses,  are  of  Asiatic  an- 
cestry, though  our  domestic  species  comes  from  Arabia  and  Africa, 
while  the  most  primitive  of  the  horses  yet  living  found  their  refuge  in 
Africa. 

Southern  or  central  Asia  was  the  birthplace  in  early  Pliocene  times 
of  the  elephants,  and  was  their  dispersal  center;  and,  in  Elephas  indi- 
cus,  the  only  domesticated  species,  we  have  the  last  and  highest  stage  in 
the  evolution  of  the  Proboscidea,  and,  as  is  the  case  with  the  cape 
buffalo,  the  zebras,  wart  hogs  and  others,  we  find  in  Africa  their  only 
living  kin,  of  more  primitive  form  and  untamable. 

Of  all  the  great  order  of  Carnivora  the  genus  Felis  admittedly  oc- 
cupies the  highest  place.  The  home  of  the  cats  is  southern  Asia  and 
there  doubtless  was  their  birthplace  and  the  center  of  their  dispersal. 
The  known  paleontological  record  of  the  true  cats  is  very  meager  in- 
deed, and  doubtless  always  will  be  till  we  know  more  of  the  Pliocene 
and  Pleistocene  faunas  of  Asia.  Two  of  the  domesticated  cats,  the 
Siamese  and  the  cheetah,  are  of  immediate  Asiatic  origin,  and  our  fire- 


THE  PALEONTOLOGIC  RECORD  87 

Bide  pet,  while  coming  from  northern  Africa,  doubtless  arose  from 
Asiatic  forebears  in  Pliocene  or  Pleistocene  times.  What  the  origin  of 
the  various  strains  of  dogs  was  we  know  not,  though  the  wild  forms 
most  nearly  allied  are  living  in  Asia  to-day,  and  the  greyhound  and 
mastiff  almost  surely  were  domesticated  in  Africa  thousands  of  years 
ago.  I  believe  that  we  may  safely  give  to  Asia  the  honor  of  the  birth- 
place of  most  of  the  domesticated  species  in  Pliocene  or  Pleistocene 
times. 

Nor  does  it  seem  that  this  remarkable  evolutional  acceleration  dur- 
ing Pliocene  times  in  central  Asia  was  confined  to  the  mammals  alone. 
The  ostrich,  the  highest  type  of  ratite  birds,  arose  in  central  Asia.  The 
jungle  fowl,  the  highest  of  the  gallinaceous  birds  and  the  ancestral 
stock  of  our  most  valued  domestic  fowls,  arose  in  India  and  is  still  at 
home  there.  The  peacock  is  exclusively  Asiatic;  the  gray  goose,  the 
parent  of  our  domestic  geese,  has  its  home  in  part  at  least  in  Asia;  and 
the  same  may  be  said  of  the  ancestors  of  the  domestic  doves;  while  the 
domestic  duck  may  have  originated  there  for  aught  we  yet  know.  The 
guinea  fowls  only  are  exclusively  African,  and  the  turkey  American. 

Of  the  reptiles  I  will  venture  to  say  less.  But  is  it  not  a  significant 
fact  that  the  highest  specialization  of  the  reptilian  class  appeared  dur- 
ing Pliocene  times  in  the  gigantic  extinct  ga vials  of  central  Asia? 
Certainly  the  cobra  is  entitled  to  a  high  but  unenviable  distinction 
among  the  snakes.  And  Megalobatrachus,  the  largest  of  all  recent 
amphibians,  lives  in  Japan  and  China.  Finally,  of  the  domestic  plants 
by  far  the  majority  come  directly  or  indirectly  .from  the  Asiatic  flora. 

Have  all  these  and  doubtless  many  other  facts  of  their  kind  no 
significance  ?  Has  man  been  an  exception  among  so  many  branches  of 
vertebrate  evolution?  The  common  inference  has  been  that  so  many 
of  our  domesticated  animals  and  plants  come  from  India  because  man 
first  reached  civilization  there,  but  the  inference  is,  I  believe,  quite  un- 
justifiable. Man  was  born  and  attained  elemental  civilization  in  Asia 
because  there  was  the  place  of  all  others  upon  the  earth  where  evolu- 
tion in  general  of  organic  life  reached  its  highest  development  in  late 
Cenozoic  times.  No  mammals  and  few  other  creatures  have  been  do- 
mesticated by  man  in  thousands  of  years,  for  the  simple  reason  that  he 
had  eliminated  all  but  the  most  advanced  and  most  adaptable  long  be- 
fore, and  none  were  left  to  compete  with  them. 

That  man  originated  in  the  western  continent  is  quite  impossible. 
There  is  not  a  particle  of  evidence  in  support  of  such  an  hypothesis, 
for  there  is  no  evidence  that  either  man  OB  any  of  his  ancestry  ever 
inhabited  the  western  continent  till  late  in  Pleistocene  times.  Indeed, 
so  far  as  North  America  is  concerned,  there  is  much  to  justify  the  as- 
sertion that  the  Pliocene  and  Pleistocene  were  a  period  of  evolutional 
depression  here,  of  relative  quiescence  when  the  rhinoceroses,  tapirs, 


88  THE  PALEONTOLOGIC  RECORD 

and  later  the  camels  and  horses,  found  conditions  uncongenial  and 
migrated  to  Asia,  a  more  favored  region. 

It  has  often  been  assumed  that  man  must  have  originated  in  a 
warm  or  tropical  climate,  to  account  for  the  loss  of  his  hairy  covering. 
But  I  quite  agree  with  Dr.  Matthew,  that  the  loss  of  hair  is  almost 
conclusive  evidence  of  his  origin  in  a  temperate  or  cold  climate  where 
he  found  clothing  necessary  to  protect  himself  from  the  inclemencies 
of  the  weather.  We  know  of  no  mammals  or  birds  losing  their  pelage 
or  plumage  because  of  tropical  conditions,  though  some  may  have  lost 
their  hair  because  of  vermin. 

Taking  all  these  facts  and  conclusions  into  consideration  it  seems 
to  me  that  such  evidence  as  paleontology  can  at  the  present  time  offer 
points  toward  central  Asia  as  the  birthplace  of  Homo,  and  that  the 
time  of  his  origin,  as  a  family,  was  late  Miocene  or  early  Pliocene. 
If  Pithecanthropus  be  really  a  true  hominid,  then  we  already  have  evi- 
dence of  his  origin  in  the  Asiatic  region.  Be  it  as  it  may,  I  confidently 
believe  that  within  a  very  few  years  the  discovery  of  indubitable  links 
in  man's  ancestry  will  be  made  in  central  Asia,  in  China  or  northern 
India.  Perhaps  to  no  region  of  the  world  does  the  paleontologist  look 
with  more  eager  expectation  for  the  solution  of  many  profound  prob- 
lems in  the  phylogenies  and  migrations  of  the  mammals  than  to  central 
and  eastern  Asia.  That  there  are  remains  of  many  extinct  vertebrates 
awaiting  discovery  there  in  the  late  Tertiary  and  Pleistocene  deposits 
has  been  made  evident  by  the  many  fragments  brought  to  light  by 
explorers  and  travelers. 

A  field  second  to  none  other  in  the  importance  and  richness  of  the 
results  to  be  expected  awaits  the  paleontologist  in  Asia. 


THE   RELATION   OF   PALEONTOLOGY  TO   THE   HISTORY 

OP   MAN,  WITH   PARTICULAR   REFERENCE  TO 

THE   AMERICAN   PROBLEM 

BY   PROFESSOR  JOHN  C.   MERRIAM 

UNIVERSITY   OF  CALIFORNIA 

CONSIDERED  in  its  broadest  aspect,  the  most  important  relation 
Vy  of  paleontology  to  the  study  of  man  concerns  the  support  which 
it  gives  to  the  general  theory  of  evolution  of  the  organic  world.  If  it 
be  held  that  we  have  reason  to  believe  man,  with  all  his  highest 
qualities,  a  product  of  evolution  out  of  so-called  lower  animal^  types, 
then  it  becomes  necessary  to  have  a  full  knowledge  of  the  history  of 
man  and  of  the  forms  preceding  him,  in  order  to  understand  the  origin 
and  the  true  nature  of  man's  fundamental  characteristics  as  they  exist 
to-day.  On  the  other  hand,  if  there  is  reason  to  believe  that  man  as 


THE  PALEONTOLOGIC  RECORD  89 

represented  in  his  highest  attributes  is  entirely  apart  from  nature,  the 
importance  of  paleontology,  as  offering  a  part  of  the  explanation  of  the 
fundamental  characteristics  of  man,  is  very  greatly  diminished.  The 
value  of  paleontology  would  then  lie  largely  in  an  interpretation  of  the 
setting  or  environment  in  which  man  is  developing. 

,  With  these  considerations  in  mind,  it  appears  of  the  greatest  impor- 
tance for  us  to  obtain  as  full  a  history  of  the  organic  world,  and  as 
satisfactory  an  interpretation  of  the  processes  therein  concerned,  as  it 
is  possible  to  secure.  Particularly  is  it  desirable  to  have  before  us  a 
clear  statement  of  that  portion  of  the  paleontological  record  which 
leads  from  the  higher  vertebrates  through  the  primate  division  to  man. 

One  of  the  important  phases  of  general  paleontological  work  which 
must  receive  special  attention  is  the  early  history  of  the  primate  order 
with  particular  reference  to  the  development  of  those  characteristics 
which  are  most  prominent  in  the  human  family.  We  have,  as  yet, 
accumulated  too  little  evidence  in  this  field.  Among  the  characters 
which  must  be  followed  would  be  ( 1 )  extraordinary  brain  development, 
(2)  the  tendency  to  development  of  an  upright  position,  (3)  the  free- 
ing of  the  anterior  limbs  from  the  work  of  locomotion  and  the  develop- 
ment in  them  of  extraordinary  adaptability.  Whatever  other  interests 
one  may  have,  there  is  certainly  no  more  alluring  problem  than  tracing 
from  the  primitive  mammalia  into  the  early  primate  those  peculiar 
characters  through  which  later  on  primitive  man  began  the  process  of 
making  nature  subservient  to  himself.  We  may  never  know  whether 
the  brain  actually  grew  large  first  and  requisitioned  the  hands,  so  that 
the  animal  became  bipedal  and  therefore  finally  erect  in  position,  or 
whether  a  tendency  to  erect  position  was  directed  by  the  frequent  as- 
suming of  a  vertical  position  in  a  tree-climbing  ancestor;  but  it  is  not 
beyond  reason  to  presume  that  a  thoroughly  satisfactory  paleontological 
record  might  give  us  an  explanation  of  the  origin  of  these  characters. 

The  later  primate  history,  or  that  which  leads  directly  to  the 
human  type,  is  also  unfortunately  incomplete,  though  most  remarkable 
advances  have  been  made  in  the  last  few  years.  More  missing  links 
have  already  been  furnished  than  science  was  supposed  to  require  a 
few  decades  ago,  but  we  can  hardly  be  said  to  have  one  tenth  of  the 
material  that  it  is  desirable  to  have  in  order  to  show  the  transition  from 
anthropoid  to  human,  or  from  pithecanthropoid  to  the  type  of  Spy  or 
Neanderthal.  European  paleontologists  are  at  the  present  time  making 
rapid  strides  in  filling  the  gaps  of  that  portion  of  our  ancestral  chain 
which  falls  in  the  Quaternary  system,  and  we  may  look  for  other 
important  discoveries  within  the  next  decade. 

It  is  to  be  presumed  that  the  greater  part  of  the  work  on  the  late 
Tertiary  and  Quaternary  history  of  man  will  be  carried  on  in  the  old 
world.  The  writer  sees  no  reason  why  in  this  important  work  Amer- 


90  THE  PALEONTOLOGIC  RECORD 

ican  paleontologists  should  not  interest  themselves  to  some  extent  in 
investigations  now  in  progress  in  Europe  and  Asia,  just  as  American 
archeologists  have  contributed  to  the  success  of  work  on  the  later  his- 
tory of  man.  Whether  American  paleontologsits,  working  in  their  own 
field,  are  to  have  a  part  in  interpreting  the  Pleistocene  history  of  man 
is  a  burning  question  at  the  present  time. 

"Whether  we  find  that  man  was  in  North  America  in  Pleistocene 
time  or  not,  it  is  certainly  true  that  one  of  the  most  important  prob- 
lems in  the  general  history  of  the  human  race  concerns  the  date  of 
occupation  of  the  western  hemisphere  by  the  human  family.  Discussion 
of  the  numerous  finds  reported  to  represent  Pleistocene  man  in  North 
America  are  too  well  known  to  every  one  to  require  particular  mention. 
It  should  only  be  noted  in  passing,  that  as  yet  no  specimens  represent- 
ing either  skeletal  remains  or  implements  of  man  found  in  North 
America  are  generally  recognized  by  geologists  and  paleontologists  as 
of  Pleistocene  age.  A  careful  search  through  the  literature,  and  the 
investigation  of  many  of  the  actual  occurrences,  lead  the  writer  to  the 
conclusion  that  we  have,  as  yet,  nothing  in  North  America  which  can 
be  considered  as  unquestionably  representing  Pleistocene  man. 

Also  in  South  America  there  has  been  serious  discussion  of  many 
interesting  finds.  The  evidence  on  the  whole  seems  to  be  more  dis- 
tinctly in  favor  of  Pleistocene  occupation  there  than  is  the  case  in 
North  America.  The  discoveries  made  in  recent  years  in  the  cave  at 
Last  Hope  Inlet,  and  the  numerous  remains  found  in  the  Pampean 
formation  at  levels  very  far  below  the  surface,  seem  difficult  to  interpret 
excepting  on  the  supposition  that  man  was  present  in  South  America 
before  the  beginning  of  the  recent  epoch. 

It  is  to  be  presumed  that  any  occupation  of  South  America  would 
necessarily  be  through  migration  by  way  of  the  northern  continent,  and 
proof  of  the  presence  of  man  in  South  America  in  Pleistocene  time 
would  be  tantamount  to  proof  that  he  was  in  North  America  at  least 
as  early.  This  suggestion  does  not,  of  course,  take  into  account  the 
theories  of  Ameghino  to  the  effect  that  man  is  possibly  derived  from 
some  of  the  South  American  monkey  forms.  Another  suggestion  made 
by  Ameghino  would  give  us  an  immigration  of  old  world  forms,  pos- 
sibly with  ancestral  man,  coming  into  the  southern  continent  in  com- 
paratively late  time,  by  some  other  route  than  North  America. 

In  the  consideration  of  man's  history  in  America,  it  is  particularly 
important  to  notice  the  probable  relation  of  migrations  of  the  human 
family  to  migrations  of  other  groups  of  mammals.  The  presumption 
is  that  the  migrations  of  primitive  man  were  caused  or  occasioned 
largely  by  influences  of  the  same  sort  as  have  produced  the  spreading 
out  or  migration  of  many  other  mammalian  types.  It  becomes  then 
particularly  necessary  to  discover  exactly  when  the  more  recent  migra- 


THE  PALEONTOLOGIC  RECORD  91 

tions  of  mammals  into  the  North  American  continent  have  taken  place, 
and,  so  far  as  possible,  the  exact  routes  of  migration.  This  problem  is 
in  a  large  part  paleontological,  requiring  for  its  interpretation  a  satis- 
factory account  of  the  paleontology  of  vertebrates,  invertebrates  and 
plants  of  North  America  and  of  Asia,  with  particular  reference  to  the 
relations  of  adjacent  areas.  We  must  also  have,  associated  with  this 
information,  a  full  statement  of  the  crustal  movements  in  these  regions 
as  interpreted  by  the  stratigraphic  geologists  and  the  physiographers. 

Through  the  accumulated  efforts  of  paleontologists  in  this  country 
particularly,  we  have  already  a  considerable  mass  of  evidence  bearing 
on  the  general  relationships  of  the  faunas  of  North  America  and  Asia 
in  comparatively  recent  geological  time,  but  the  detail  of  the  problem 
is,  as  yet,  scarcely  indicated.  Particularly  for  Pleistocene  and  Pliocene 
time  our  knowledge  of  the  faunal  succession  is  exceedingly  meager,  and 
we  can  scarcely  expect  to  know  anything  satisfactorily  until  the  Pleisto- 
cene mammalian  paleontology  of  America  has  been  worked  out  in 
detail.  This  work  must  be  followed  or  accompanied  by  similar  studies 
of  the  mammalian  faunas  of  western  and  southern  Asia.  When  this  is 
completed  we  shall  know  the  time  of  the  various  migratory  movements, 
the  nature  of  the  faunas  which  migrated,  the  character  of  the  land  areas 
over  which  they  have  passed,  and  the  climatic  conditions  which  obtained 
along  the  routes  of  migration.  The  presumption  is,  that  when  this  is 
done  we  shall  have  actual  evidence  of  the  time  of  man's  occupation  of 
North  America. 

Viewed  in  the  large,  and  without  regard  to  the  detail  which  has 
just  been  indicated,  it  seems  possible  to  present  several  reasonable 
conclusions  with  reference  to  the  probable  period  of  migration  of  man 
to  America.  It  is  shown  by  study  of  a  map  of  linguistic  stocks  of  the 
western  hemisphere  that  the  northern  and  southern  continents  taken 
together  may  be  divided  into  between  one  hundred  and  two  hundred 
provinces,  based  on  the  number  of  stocks  represented.  These  lan- 
guages vary  greatly  in  their  structure,  and  are  not  similar  to  the 
languages  of  other  parts  of  the  world.  There  is  every  reason  to 
believe  that  a  large  percentage  of  them  have  been  developed  by  lin- 
guistic differentiation  which  occurred  since  man  first  occupied  this  con- 
tinent, and  that  measured  in  years  the  time  required  for  this  differentia- 
tion has  been  long.  On  the  other  hand,  considering  the  American  con- 
tinent as  a'  whole,  we  find  that  the  greatly  differing  physical  environ- 
ments are  not  reflected  to  any  extent  in  different  physical  types  of  people 
occupying  this  region.  That  the  human  family  is  not  exempt  from 
physical  differentiation,  such  as  is  almost  universally  indicated  in  mam- 
mals which  have  for  some  time  been  distributed  over  large  areas  with 
varying  environments,  is  clearly  shown  by  the  map  of  the  old  world. 
In  that  region  the  human  race  is  known  to  have  been  spread  over  a  wide 


92  THE  PALEONTOLOGIC  RECORD 

area  for  a  long  period,  and  we  find  several  greatly  differing  human 
physical  stocks  in  different  geographic  regions,  just  as  we  find  differing 
stocks  of  mammals  and  birds. 

With  the  lack  of  physical  diversity  among  the  people  of  the  western 
hemisphere,  there  is  also  noticeable  a  resemblance  of  the  whole  group 
to  the  people  of  the  adjacent  region  of  Asia.  Judged  by  the  standards 
of  differentiation  which  we  obtain  through  a  study  of  the  history  of 
geographical  distribution  of  other  mammalian  groups,  we  have  every 
reason  to  think  that  the  people  of  America  are  immigrants  who  came 
from  the  Asiatic  region  and  spread  themselves  over  America  after  the 
period  of  the  first  great  physical  differentiation  of  the  race,  and  so 
recently  that  a  second  stage  of  physical  differentiation  has  not  yet  had 
time  to  develop.  On  the  other  hand,  the  time  measured  in  years  has 
been  long  enough  so  that  linguistic  differentiation  could  take  place. 

Inasmuch  as  a  large  part  of  human  history  falls  within  the  Quater- 
nary period,  the  question  naturally  arises  as  to  whether  the  principal 
migrations  of  man  to  the  American  continent  occurred  before,  during 
or  after  the  Glacial  epoch. 

As  primates  are  naturally  animals  of  a  warm  or  temperate  zone, 
it  is  hardly  to  be  presumed  that  primitive  man  came  to  America  during 
the  ice  age,  though  there  is  a  possibility  of  immigration  in  some  of  the 
interglacial  epochs.  Judging  from  what  is  suggested  through  study  of 
physical  differentiation,  it  appears  improbable  that  man  came  over  as 
early  as  the  epoch  preceding  the  ice  age.  In  other  groups  of  animals 
spread  over  large  areas,  marked  physical  differentiation  has  ordinarily 
taken  place  in  a  space  of  time  comparable  to  the  Glacial  epoch.  Had 
man  been  present  in  America  during  this  long  period,  widely  differing 
physical  types  would  almost  certainly  have  developed.  On  the  whole  it 
seems  most  probable  that  he  arrived  after  the  end  of  the  last  division 
of  glacial  time,  or  very  near  the  beginning  of  the  present  epoch. 
Whether  his  arrival  is  shown  to  have  occurred  just  before  or  just  after 
the  beginning  of  this  epoch  remains  to  be  determined. 

In  conclusion  it  seems  desirable  to  call  the  attention  of  paleontolo- 
gists once  more  to  the  important  part  which  their  work  must  play  in 
obtaining  the  information  which  we  need  with  reference  to  the  history 
of  man  and  his  antecedents.  Only  a  small  beginning  has  been  made, 
and  the  results  which  must  come  are  of  great  importance  in  the  large 
problem  of  man's  relation  to  nature.  It  is  necessary  that  paleontolo- 
gists keep  the  subject  before  them,  in  order  to  make  certain  that  all 
information  bearing  upon  it  may  be  recognized  as  it  becomes  available, 
and  be  given  its  proper  place  in  relation  to  other  evidence  now  at  hand. 


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